20157681 has 16 divisors (see below), whose sum is σ = 27554688. Its totient is φ = 13104000.

The previous prime is 20157679. The next prime is 20157707. The reversal of 20157681 is 18675102.

It is not a de Polignac number, because 20157681 - 2¹ = 20157679 is a prime.

It is a super-2 number, since 2×20157681² = 812664206595522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20156681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21045 + ... + 21981.

It is an arithmetic number, because the mean of its divisors is an integer number (1722168).

Almost surely, 2^20157681 is an apocalyptic number.

It is an amenable number.

20157681 is a deficient number, since it is larger than the sum of its proper divisors (7397007).

20157681 is a wasteful number, since it uses less digits than its factorization.

20157681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1112.

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 20157681 is about 4489.7306155269. The cubic root of 20157681 is about 272.1532485967.

The spelling of 20157681 in words is "twenty million, one hundred fifty-seven thousand, six hundred eighty-one".