21001564020 has 24 divisors (see below), whose sum is σ = 58804379424. Its totient is φ = 5600417056.

The previous prime is 21001564009. The next prime is 21001564021. The reversal of 21001564020 is 2046510012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001564021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175012974 + ... + 175013093.

It is an arithmetic number, because the mean of its divisors is an integer number (2450182476).

Almost surely, 2^21001564020 is an apocalyptic number.

21001564020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001564020 is an abundant number, since it is smaller than the sum of its proper divisors (37802815404).

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

21001564020 is a wasteful number, since it uses less digits than its factorization.

21001564020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 350026079 (or 350026077 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The spelling of 21001564020 in words is "twenty-one billion, one million, five hundred sixty-four thousand, twenty".