21731457 has 16 divisors (see below), whose sum is σ = 33469632. Its totient is φ = 12395520.

The previous prime is 21731453. The next prime is 21731473. The reversal of 21731457 is 75413712.

It is not a de Polignac number, because 21731457 - 2² = 21731453 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21731453) 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, 18808 + ... + 19929.

It is an arithmetic number, because the mean of its divisors is an integer number (2091852).

Almost surely, 2^21731457 is an apocalyptic number.

It is an amenable number.

21731457 is a deficient number, since it is larger than the sum of its proper divisors (11738175).

21731457 is a wasteful number, since it uses less digits than its factorization.

21731457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38768.

The product of its digits is 5880, while the sum is 30.

The square root of 21731457 is about 4661.7010843682. The cubic root of 21731457 is about 279.0591593566.

The spelling of 21731457 in words is "twenty-one million, seven hundred thirty-one thousand, four hundred fifty-seven".