2021565605721 has 16 divisors (see below), whose sum is σ = 2726507692800. Its totient is φ = 1332175864448.

The previous prime is 2021565605707. The next prime is 2021565605737. The reversal of 2021565605721 is 1275065651202.

It is a cyclic number.

It is not a de Polignac number, because 2021565605721 - 2³³ = 2012975671129 is a prime.

It is a super-3 number, since 3×2021565605721³ (a number of 38 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (2021565605921) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 201486 + ... + 2020823.

It is an arithmetic number, because the mean of its divisors is an integer number (170406730800).

Almost surely, 2^{2021565605721} is an apocalyptic number.

It is an amenable number.

2021565605721 is a deficient number, since it is larger than the sum of its proper divisors (704942087079).

2021565605721 is a wasteful number, since it uses less digits than its factorization.

2021565605721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2225808.

The product of its (nonzero) digits is 252000, while the sum is 42.

The spelling of 2021565605721 in words is "two trillion, twenty-one billion, five hundred sixty-five million, six hundred five thousand, seven hundred twenty-one".