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21157681 = 414911051
BaseRepresentation
bin101000010110…
…1011100110001
31110210220212211
41100231130301
520404021211
62033252121
7344560126
oct120553461
943726784
1021157681
1110a41096
127104041
1344ca34c
142b4a74d
151ccde21
hex142d731

21157681 has 8 divisors (see below), whose sum is σ = 21738528. Its totient is φ = 20580000.

The previous prime is 21157649. The next prime is 21157693. The reversal of 21157681 is 18675112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21157681 - 25 = 21157649 is a prime.

It is a super-2 number, since 2×211576812 = 895294930595522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21157601) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19606 + ... + 20656.

It is an arithmetic number, because the mean of its divisors is an integer number (2717316).

Almost surely, 221157681 is an apocalyptic number.

It is an amenable number.

21157681 is a deficient number, since it is larger than the sum of its proper divisors (580847).

21157681 is a wasteful number, since it uses less digits than its factorization.

21157681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1583.

The product of its digits is 3360, while the sum is 31.

The square root of 21157681 is about 4599.7479278760. The cubic root of 21157681 is about 276.5812202060.

The spelling of 21157681 in words is "twenty-one million, one hundred fifty-seven thousand, six hundred eighty-one".

Divisors: 1 41 491 1051 20131 43091 516041 21157681