21381812 has 12 divisors (see below), whose sum is σ = 39045216. Its totient is φ = 10226040.

The previous prime is 21381791. The next prime is 21381823. The reversal of 21381812 is 21818312.

It is a congruent 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, 116114 + ... + 116297.

It is an arithmetic number, because the mean of its divisors is an integer number (3253768).

Almost surely, 2^21381812 is an apocalyptic number.

It is an amenable number.

21381812 is a deficient number, since it is larger than the sum of its proper divisors (17663404).

21381812 is a wasteful number, since it uses less digits than its factorization.

21381812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 232438 (or 232436 counting only the distinct ones).

The product of its digits is 768, while the sum is 26.

The square root of 21381812 is about 4624.0471450884. The cubic root of 21381812 is about 277.5544334957.

The spelling of 21381812 in words is "twenty-one million, three hundred eighty-one thousand, eight hundred twelve".