21353606644565 has 16 divisors (see below), whose sum is σ = 27611691570288. Its totient is φ = 15759524960256.

The previous prime is 21353606644553. The next prime is 21353606644567. The reversal of 21353606644565 is 56544660635312.

It can be written as a sum of positive squares in 8 ways, for example, as 2366262286756 + 18987344357809 = 1538266^2 + 4357447^2 .

It is a cyclic number.

It is not a de Polignac number, because 21353606644565 - 2¹² = 21353606640469 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21353606644565.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21353606644567) 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, 96683162 + ... + 96903771.

It is an arithmetic number, because the mean of its divisors is an integer number (1725730723143).

Almost surely, 2^{21353606644565} is an apocalyptic number.

It is an amenable number.

21353606644565 is a deficient number, since it is larger than the sum of its proper divisors (6258084925723).

21353606644565 is a wasteful number, since it uses less digits than its factorization.

21353606644565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193588648.

The product of its (nonzero) digits is 46656000, while the sum is 56.

The spelling of 21353606644565 in words is "twenty-one trillion, three hundred fifty-three billion, six hundred six million, six hundred forty-four thousand, five hundred sixty-five".