21511312 has 10 divisors (see below), whose sum is σ = 41678198. Its totient is φ = 10755648.

The previous prime is 21511271. The next prime is 21511327. The reversal of 21511312 is 21311512.

It can be written as a sum of positive squares in only one way, i.e., 20939776 + 571536 = 4576^2 + 756^2 .

It is a super-2 number, since 2×21511312² = 925473087922688, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (16), and also a Moran number because the ratio is a prime number: 1344457 = 21511312 / (2 + 1 + 5 + 1 + 1 + 3 + 1 + 2).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 672213 + ... + 672244.

Almost surely, 2^21511312 is an apocalyptic number.

It is an amenable number.

21511312 is a deficient number, since it is larger than the sum of its proper divisors (20166886).

21511312 is a wasteful number, since it uses less digits than its factorization.

21511312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1344465 (or 1344459 counting only the distinct ones).

The product of its digits is 60, while the sum is 16.

The square root of 21511312 is about 4638.0288916737. The cubic root of 21511312 is about 278.1136467528.

Adding to 21511312 its reverse (21311512), we get a palindrome (42822824).

The spelling of 21511312 in words is "twenty-one million, five hundred eleven thousand, three hundred twelve".