21709812 has 48 divisors (see below), whose sum is σ = 52157952. Its totient is φ = 7025760.

The previous prime is 21709781. The next prime is 21709813. The reversal of 21709812 is 21890712.

It is a self number, because there is not a number n which added to its sum of digits gives 21709812.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21709813) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 70563 + ... + 70869.

It is an arithmetic number, because the mean of its divisors is an integer number (1086624).

Almost surely, 2^21709812 is an apocalyptic number.

It is an amenable number.

21709812 is an abundant number, since it is smaller than the sum of its proper divisors (30448140).

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

21709812 is a wasteful number, since it uses less digits than its factorization.

21709812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 468 (or 466 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21709812 is about 4659.3789285698. The cubic root of 21709812 is about 278.9664789316.

The spelling of 21709812 in words is "twenty-one million, seven hundred nine thousand, eight hundred twelve".