21903812 has 24 divisors (see below), whose sum is σ = 43942080. Its totient is φ = 9358560.

The previous prime is 21903811. The next prime is 21903821. The reversal of 21903812 is 21830912.

It is not an unprimeable number, because it can be changed into a prime (21903811) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9887 + ... + 11897.

It is an arithmetic number, because the mean of its divisors is an integer number (1830920).

Almost surely, 2^21903812 is an apocalyptic number.

It is an amenable number.

21903812 is an abundant number, since it is smaller than the sum of its proper divisors (22038268).

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

21903812 is a wasteful number, since it uses less digits than its factorization.

21903812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2411 (or 2409 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21903812 is about 4680.1508522696. The cubic root of 21903812 is about 279.7949689495.

Subtracting from 21903812 its reverse (21830912), we obtain a square (72900 = 270²).

The spelling of 21903812 in words is "twenty-one million, nine hundred three thousand, eight hundred twelve".