21821812 has 36 divisors (see below), whose sum is σ = 41604640. Its totient is φ = 10007424.

The previous prime is 21821797. The next prime is 21821819. The reversal of 21821812 is 21812812.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21821819) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 49489 + ... + 49927.

Almost surely, 2^21821812 is an apocalyptic number.

It is an amenable number.

21821812 is a deficient number, since it is larger than the sum of its proper divisors (19782828).

21821812 is a wasteful number, since it uses less digits than its factorization.

21821812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 520 (or 501 counting only the distinct ones).

The product of its digits is 512, while the sum is 25.

The square root of 21821812 is about 4671.3822365548. The cubic root of 21821812 is about 279.4453817407.

It can be divided in two parts, 218218 and 12, that multiplied together give a triangular number (2618616 = T₂₂₈₈).

The spelling of 21821812 in words is "twenty-one million, eight hundred twenty-one thousand, eight hundred twelve".