21457971 has 12 divisors (see below), whose sum is σ = 31153200. Its totient is φ = 14232240.

The previous prime is 21457967. The next prime is 21457981. The reversal of 21457971 is 17975412.

It is a happy number.

21457971 is a `hidden beast` number, since 2 + 14 + 579 + 71 = 666.

It is not a de Polignac number, because 21457971 - 2² = 21457967 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21457981) 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, 4200 + ... + 7781.

It is an arithmetic number, because the mean of its divisors is an integer number (2596100).

Almost surely, 2^21457971 is an apocalyptic number.

21457971 is a deficient number, since it is larger than the sum of its proper divisors (9695229).

21457971 is a wasteful number, since it uses less digits than its factorization.

21457971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12186 (or 12183 counting only the distinct ones).

The product of its digits is 17640, while the sum is 36.

The square root of 21457971 is about 4632.2749270742. The cubic root of 21457971 is about 277.8835796016.

It can be divided in two parts, 214 and 57971, that added together give a palindrome (58185).

The spelling of 21457971 in words is "twenty-one million, four hundred fifty-seven thousand, nine hundred seventy-one".