21387612 has 12 divisors (see below), whose sum is σ = 49904456. Its totient is φ = 7129200.

The previous prime is 21387601. The next prime is 21387617. The reversal of 21387612 is 21678312.

It is a tau number, because it is divible by the number of its divisors (12).

It is a plaindrome in base 13.

It is a self number, because there is not a number n which added to its sum of digits gives 21387612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387617) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 891139 + ... + 891162.

Almost surely, 2^21387612 is an apocalyptic number.

It is an amenable number.

21387612 is an abundant number, since it is smaller than the sum of its proper divisors (28516844).

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

21387612 is a wasteful number, since it uses less digits than its factorization.

21387612 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1782308 (or 1782306 counting only the distinct ones).

The product of its digits is 4032, while the sum is 30.

The square root of 21387612 is about 4624.6742587992. The cubic root of 21387612 is about 277.5795275675.

The spelling of 21387612 in words is "twenty-one million, three hundred eighty-seven thousand, six hundred twelve".