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999991000021 = 13243323775749
BaseRepresentation
bin11101000110101000001…
…10111011101111010101
310112121011002111011211111
432203110012323233111
5112340440144000041
62043220045335021
7132150465153016
oct16432406735725
93477132434744
10999991000021
113561039390a2
1214197ab67471
13733b6467200
143658518300d
151b02aa89981
hexe8d41bbbd5

999991000021 has 24 divisors (see below), whose sum is σ = 1085976717000. Its totient is φ = 920389257216.

The previous prime is 999991000003. The next prime is 999991000103. The reversal of 999991000021 is 120000199999.

It can be written as a sum of positive squares in 12 ways, for example, as 965954808900 + 34036191121 = 982830^2 + 184489^2 .

It is not a de Polignac number, because 999991000021 - 27 = 999990999893 is a prime.

It is the 999996-th Hogben number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999991000721) by changing a digit.

It is a nontrivial repunit in base 999995.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 173938855 + ... + 173944603.

It is an arithmetic number, because the mean of its divisors is an integer number (45249029875).

Almost surely, 2999991000021 is an apocalyptic number.

It is an amenable number.

999991000021 is a deficient number, since it is larger than the sum of its proper divisors (85985716979).

999991000021 is a wasteful number, since it uses less digits than its factorization.

999991000021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8585 (or 8572 counting only the distinct ones).

The product of its (nonzero) digits is 118098, while the sum is 49.

The spelling of 999991000021 in words is "nine hundred ninety-nine billion, nine hundred ninety-one million, twenty-one", and thus it is an aban number.

Divisors: 1 13 169 433 2377 5629 5749 30901 73177 74737 401713 971581 1029241 2489317 13380133 13665373 32361121 173941729 177649849 420694573 2309448037 5917106509 76922384617 999991000021