20921569965 has 12 divisors (see below), whose sum is σ = 36264054684. Its totient is φ = 11158170624.

The previous prime is 20921569939. The next prime is 20921569967. The reversal of 20921569965 is 56996512902.

It can be written as a sum of positive squares in 2 ways, for example, as 12223955844 + 8697614121 = 110562^2 + 93261^2 .

It is not a de Polignac number, because 20921569965 - 2¹⁷ = 20921438893 is a prime.

It is a super-3 number, since 3×20921569965³ (a number of 32 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20921569967) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 232461844 + ... + 232461933.

It is an arithmetic number, because the mean of its divisors is an integer number (3022004557).

Almost surely, 2^20921569965 is an apocalyptic number.

It is an amenable number.

20921569965 is a deficient number, since it is larger than the sum of its proper divisors (15342484719).

20921569965 is a wasteful number, since it uses less digits than its factorization.

20921569965 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 464923788 (or 464923785 counting only the distinct ones).

The product of its (nonzero) digits is 2624400, while the sum is 54.

The spelling of 20921569965 in words is "twenty billion, nine hundred twenty-one million, five hundred sixty-nine thousand, nine hundred sixty-five".