21305964 has 48 divisors (see below), whose sum is σ = 53415936. Its totient is φ = 6585600.

The previous prime is 21305939. The next prime is 21305983. The reversal of 21305964 is 46950312.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13749 + ... + 15219.

It is an arithmetic number, because the mean of its divisors is an integer number (1112832).

Almost surely, 2^21305964 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21305964, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26707968).

21305964 is an abundant number, since it is smaller than the sum of its proper divisors (32109972).

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

21305964 is a wasteful number, since it uses less digits than its factorization.

21305964 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1566 (or 1564 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 30.

The square root of 21305964 is about 4615.8383853857. The cubic root of 21305964 is about 277.2258537591.

It can be divided in two parts, 2130 and 5964, that multiplied together give a triangular number (12703320 = T₅₀₄₀).

The spelling of 21305964 in words is "twenty-one million, three hundred five thousand, nine hundred sixty-four".