21257131 has 12 divisors (see below), whose sum is σ = 24913560. Its totient is φ = 18083520.

The previous prime is 21257107. The next prime is 21257141. The reversal of 21257131 is 13175212.

It is a happy number.

It is not a de Polignac number, because 21257131 - 2⁷ = 21257003 is a prime.

It is a super-2 number, since 2×21257131² = 903731236702322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21257101) 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, 5251 + ... + 8371.

It is an arithmetic number, because the mean of its divisors is an integer number (2076130).

Almost surely, 2^21257131 is an apocalyptic number.

21257131 is a deficient number, since it is larger than the sum of its proper divisors (3656429).

21257131 is a wasteful number, since it uses less digits than its factorization.

21257131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3274 (or 3267 counting only the distinct ones).

The product of its digits is 420, while the sum is 22.

The square root of 21257131 is about 4610.5456293155. The cubic root of 21257131 is about 277.0138923554.

The spelling of 21257131 in words is "twenty-one million, two hundred fifty-seven thousand, one hundred thirty-one".