21620564 has 36 divisors (see below), whose sum is σ = 44968896. Its totient is φ = 9064944.

The previous prime is 21620563. The next prime is 21620569. The reversal of 21620564 is 46502612.

21620564 = T₂₂₇ + T₂₂₈ + ... + T₅₂₀.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21620561) 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 11 ways as a sum of consecutive naturals, for example, 8039 + ... + 10385.

It is an arithmetic number, because the mean of its divisors is an integer number (1249136).

Almost surely, 2^21620564 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 21620564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22484448).

21620564 is an abundant number, since it is smaller than the sum of its proper divisors (23348332).

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

21620564 is a wasteful number, since it uses less digits than its factorization.

21620564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2412 (or 2403 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21620564 is about 4649.7918232970. The cubic root of 21620564 is about 278.5836812744.

The spelling of 21620564 in words is "twenty-one million, six hundred twenty thousand, five hundred sixty-four".