21208964 has 36 divisors (see below), whose sum is σ = 43451100. Its totient is φ = 9031680.

The previous prime is 21208961. The next prime is 21208969. The reversal of 21208964 is 46980212.

21208964 = T₂₁ + T₂₂ + ... + T₅₀₂.

It can be written as a sum of positive squares in 2 ways, for example, as 14500864 + 6708100 = 3808^2 + 2590^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21208964.

It is not an unprimeable number, because it can be changed into a prime (21208961) 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, 47012 + ... + 47460.

It is an arithmetic number, because the mean of its divisors is an integer number (1206975).

Almost surely, 2^21208964 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 21208964, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21725550).

21208964 is an abundant number, since it is smaller than the sum of its proper divisors (22242136).

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

21208964 is a wasteful number, since it uses less digits than its factorization.

21208964 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 708 (or 699 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 32.

The square root of 21208964 is about 4605.3190986076. The cubic root of 21208964 is about 276.8045035019.

The spelling of 21208964 in words is "twenty-one million, two hundred eight thousand, nine hundred sixty-four".