21312657 has 24 divisors (see below), whose sum is σ = 31571904. Its totient is φ = 13850784.

The previous prime is 21312647. The next prime is 21312671. The reversal of 21312657 is 75621312.

It is a happy number.

21312657 is a `hidden beast` number, since 2 + 1 + 3 + 1 + 2 + 657 = 666.

It is not a de Polignac number, because 21312657 - 2¹⁴ = 21296273 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21312657.

It is not an unprimeable number, because it can be changed into a prime (21312647) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 76803 + ... + 77079.

It is an arithmetic number, because the mean of its divisors is an integer number (1315496).

Almost surely, 2^21312657 is an apocalyptic number.

It is an amenable number.

21312657 is a deficient number, since it is larger than the sum of its proper divisors (10259247).

21312657 is a wasteful number, since it uses less digits than its factorization.

21312657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 469 (or 466 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 21312657 is about 4616.5633321769. The cubic root of 21312657 is about 277.2548797223.

Adding to 21312657 its reverse (75621312), we get a palindrome (96933969).

The spelling of 21312657 in words is "twenty-one million, three hundred twelve thousand, six hundred fifty-seven".