21651312 has 20 divisors (see below), whose sum is σ = 55932680. Its totient is φ = 7217088.

The previous prime is 21651307. The next prime is 21651323. The reversal of 21651312 is 21315612.

It is a super-2 number, since 2×21651312² = 937558622642688, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 225487 + ... + 225582.

It is an arithmetic number, because the mean of its divisors is an integer number (2796634).

Almost surely, 2^21651312 is an apocalyptic number.

It is an amenable number.

21651312 is an abundant number, since it is smaller than the sum of its proper divisors (34281368).

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

21651312 is a wasteful number, since it uses less digits than its factorization.

21651312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 451080 (or 451074 counting only the distinct ones).

The product of its digits is 360, while the sum is 21.

The square root of 21651312 is about 4653.0970331597. The cubic root of 21651312 is about 278.7156826649.

Adding to 21651312 its reverse (21315612), we get a palindrome (42966924).

The spelling of 21651312 in words is "twenty-one million, six hundred fifty-one thousand, three hundred twelve".