21320864 has 12 divisors (see below), whose sum is σ = 41975514. Its totient is φ = 10660416.

The previous prime is 21320863. The next prime is 21320867. The reversal of 21320864 is 46802312.

It can be written as a sum of positive squares in only one way, i.e., 13987600 + 7333264 = 3740^2 + 2708^2 .

It is not an unprimeable number, because it can be changed into a prime (21320863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333107 + ... + 333170.

Almost surely, 2^21320864 is an apocalyptic number.

It is an amenable number.

21320864 is a deficient number, since it is larger than the sum of its proper divisors (20654650).

21320864 is an equidigital number, since it uses as much as digits as its factorization.

21320864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 666287 (or 666279 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 26.

The square root of 21320864 is about 4617.4521112839. The cubic root of 21320864 is about 277.2904632535.

The spelling of 21320864 in words is "twenty-one million, three hundred twenty thousand, eight hundred sixty-four".