21308816 has 10 divisors (see below), whose sum is σ = 41285862. Its totient is φ = 10654400.

The previous prime is 21308801. The next prime is 21308831. The reversal of 21308816 is 61880312.

It is an interprime number because it is at equal distance from previous prime (21308801) and next prime (21308831).

It can be written as a sum of positive squares in only one way, i.e., 19360000 + 1948816 = 4400^2 + 1396^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 665885 + ... + 665916.

Almost surely, 2^21308816 is an apocalyptic number.

It is an amenable number.

21308816 is a deficient number, since it is larger than the sum of its proper divisors (19977046).

21308816 is a wasteful number, since it uses less digits than its factorization.

21308816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1331809 (or 1331803 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 21308816 is about 4616.1473113409. The cubic root of 21308816 is about 277.2382229539.

The spelling of 21308816 in words is "twenty-one million, three hundred eight thousand, eight hundred sixteen".