21157696 has 56 divisors (see below), whose sum is σ = 48646080. Its totient is φ = 8942592.

The previous prime is 21157693. The next prime is 21157699. The reversal of 21157696 is 69675112.

It is an interprime number because it is at equal distance from previous prime (21157693) and next prime (21157699).

It is a tau number, because it is divible by the number of its divisors (56).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21157693) 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, 36900 + ... + 37468.

It is an arithmetic number, because the mean of its divisors is an integer number (868680).

Almost surely, 2^21157696 is an apocalyptic number.

21157696 is the 2656-th octagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21157696, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24323040).

21157696 is an abundant number, since it is smaller than the sum of its proper divisors (27488384).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21157696 is an equidigital number, since it uses as much as digits as its factorization.

21157696 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 671 (or 661 counting only the distinct ones).

The product of its digits is 22680, while the sum is 37.

The square root of 21157696 is about 4599.7495583999. The cubic root of 21157696 is about 276.5812855679.

The spelling of 21157696 in words is "twenty-one million, one hundred fifty-seven thousand, six hundred ninety-six".