21531368 has 8 divisors (see below), whose sum is σ = 40371330. Its totient is φ = 10765680.

The previous prime is 21531361. The next prime is 21531379. The reversal of 21531368 is 86313512.

It can be written as a sum of positive squares in only one way, i.e., 14760964 + 6770404 = 3842^2 + 2602^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21531368.

It is not an unprimeable number, because it can be changed into a prime (21531361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1345703 + ... + 1345718.

Almost surely, 2^21531368 is an apocalyptic number.

It is an amenable number.

21531368 is a deficient number, since it is larger than the sum of its proper divisors (18839962).

21531368 is a wasteful number, since it uses less digits than its factorization.

21531368 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2691427 (or 2691423 counting only the distinct ones).

The product of its digits is 4320, while the sum is 29.

The square root of 21531368 is about 4640.1905133302. The cubic root of 21531368 is about 278.2000526820.

The spelling of 21531368 in words is "twenty-one million, five hundred thirty-one thousand, three hundred sixty-eight".