20157921 has 12 divisors (see below), whose sum is σ = 33276672. Its totient is φ = 11518776.

The previous prime is 20157911. The next prime is 20157923. The reversal of 20157921 is 12975102.

It is not a de Polignac number, because 20157921 - 2⁵ = 20157889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20157923) 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 11 ways as a sum of consecutive naturals, for example, 159921 + ... + 160046.

It is an arithmetic number, because the mean of its divisors is an integer number (2773056).

Almost surely, 2^20157921 is an apocalyptic number.

20157921 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20157921 is a deficient number, since it is larger than the sum of its proper divisors (13118751).

20157921 is a wasteful number, since it uses less digits than its factorization.

20157921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319980 (or 319977 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 20157921 is about 4489.7573431089. The cubic root of 20157921 is about 272.1543286899.

The spelling of 20157921 in words is "twenty million, one hundred fifty-seven thousand, nine hundred twenty-one".