21531272 has 16 divisors (see below), whose sum is σ = 46138560. Its totient is φ = 9227664.

The previous prime is 21531269. The next prime is 21531317. The reversal of 21531272 is 27213512.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 192188 + ... + 192299.

It is an arithmetic number, because the mean of its divisors is an integer number (2883660).

Almost surely, 2^21531272 is an apocalyptic number.

It is an amenable number.

21531272 is an abundant number, since it is smaller than the sum of its proper divisors (24607288).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21531272 is a wasteful number, since it uses less digits than its factorization.

21531272 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 384500 (or 384496 counting only the distinct ones).

The product of its digits is 840, while the sum is 23.

The square root of 21531272 is about 4640.1801689159. The cubic root of 21531272 is about 278.1996392194.

Adding to 21531272 its reverse (27213512), we get a palindrome (48744784).

The spelling of 21531272 in words is "twenty-one million, five hundred thirty-one thousand, two hundred seventy-two".