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21417991 = 723151881
BaseRepresentation
bin101000110110…
…1000000000111
31111022010221221
41101231000013
520440333431
62043021211
7350023060
oct121550007
944263857
1021417991
11110a9721
12720a807
13458b98a
142bb7567
151d31111
hex146d007

21417991 has 16 divisors (see below), whose sum is σ = 25740288. Its totient is φ = 17424000.

The previous prime is 21417973. The next prime is 21418009. The reversal of 21417991 is 19971412.

It is an interprime number because it is at equal distance from previous prime (21417973) and next prime (21418009).

It is a 7-Lehmer number, since φ(21417991) divides (21417991-1)7.

It is a cyclic number.

It is not a de Polignac number, because 21417991 - 217 = 21286919 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21417971) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 23871 + ... + 24751.

It is an arithmetic number, because the mean of its divisors is an integer number (1608768).

It is a Poulet number, since it divides 221417990-1.

Almost surely, 221417991 is an apocalyptic number.

21417991 is a deficient number, since it is larger than the sum of its proper divisors (4322297).

21417991 is a wasteful number, since it uses less digits than its factorization.

21417991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1062.

The product of its digits is 4536, while the sum is 34.

The square root of 21417991 is about 4627.9575408597. The cubic root of 21417991 is about 277.7108902003.

The spelling of 21417991 in words is "twenty-one million, four hundred seventeen thousand, nine hundred ninety-one".

Divisors: 1 7 23 151 161 881 1057 3473 6167 20263 24311 133031 141841 931217 3059713 21417991