21621964 has 48 divisors (see below), whose sum is σ = 46964736. Its totient is φ = 8481600.

The previous prime is 21621961. The next prime is 21621967. The reversal of 21621964 is 46912612.

It is an interprime number because it is at equal distance from previous prime (21621961) and next prime (21621967).

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21621961) 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, 69369 + ... + 69679.

It is an arithmetic number, because the mean of its divisors is an integer number (978432).

Almost surely, 2^21621964 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 21621964, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23482368).

21621964 is an abundant number, since it is smaller than the sum of its proper divisors (25342772).

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

21621964 is a wasteful number, since it uses less digits than its factorization.

21621964 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 526 (or 524 counting only the distinct ones).

The product of its digits is 5184, while the sum is 31.

The square root of 21621964 is about 4649.9423652342. The cubic root of 21621964 is about 278.5896942032.

The spelling of 21621964 in words is "twenty-one million, six hundred twenty-one thousand, nine hundred sixty-four".