21157081 has 16 divisors (see below), whose sum is σ = 23912640. Its totient is φ = 18550080.

The previous prime is 21157067. The next prime is 21157091. The reversal of 21157081 is 18075112.

It is a cyclic number.

It is not a de Polignac number, because 21157081 - 2⁵ = 21157049 is a prime.

It is a super-2 number, since 2×21157081² = 895244152881122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21157091) 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, 92275 + ... + 92503.

It is an arithmetic number, because the mean of its divisors is an integer number (1494540).

Almost surely, 2^21157081 is an apocalyptic number.

It is an amenable number.

21157081 is a deficient number, since it is larger than the sum of its proper divisors (2755559).

21157081 is a wasteful number, since it uses less digits than its factorization.

21157081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 504.

The product of its (nonzero) digits is 560, while the sum is 25.

The square root of 21157081 is about 4599.6827064483. The cubic root of 21157081 is about 276.5786057055.

The spelling of 21157081 in words is "twenty-one million, one hundred fifty-seven thousand, eighty-one".