21521020001 has 32 divisors (see below), whose sum is σ = 24728366880. Its totient is φ = 18553982976.

The previous prime is 21521019977. The next prime is 21521020013. The reversal of 21521020001 is 10002012512.

It can be written as a sum of positive squares in 16 ways, for example, as 18995454976 + 2525565025 = 137824^2 + 50255^2 .

It is not a de Polignac number, because 21521020001 - 2²⁶ = 21453911137 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21521020061) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 19405235 + ... + 19406343.

It is an arithmetic number, because the mean of its divisors is an integer number (772761465).

Almost surely, 2^21521020001 is an apocalyptic number.

It is an amenable number.

21521020001 is a deficient number, since it is larger than the sum of its proper divisors (3207346879).

21521020001 is a wasteful number, since it uses less digits than its factorization.

21521020001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1733.

The product of its (nonzero) digits is 40, while the sum is 14.

Adding to 21521020001 its reverse (10002012512), we get a palindrome (31523032513).

The spelling of 21521020001 in words is "twenty-one billion, five hundred twenty-one million, twenty thousand, one".