21615261853 has 8 divisors (see below), whose sum is σ = 22362265080. Its totient is φ = 20868368640.

The previous prime is 21615261823. The next prime is 21615261893. The reversal of 21615261853 is 35816251612.

It can be written as a sum of positive squares in 4 ways, for example, as 4122025209 + 17493236644 = 64203^2 + 132262^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21615261853 - 2²¹ = 21613164701 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21615261823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 688801 + ... + 719497.

It is an arithmetic number, because the mean of its divisors is an integer number (2795283135).

Almost surely, 2^21615261853 is an apocalyptic number.

It is an amenable number.

21615261853 is a deficient number, since it is larger than the sum of its proper divisors (747003227).

21615261853 is a wasteful number, since it uses less digits than its factorization.

21615261853 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55007.

The product of its digits is 86400, while the sum is 40.

The spelling of 21615261853 in words is "twenty-one billion, six hundred fifteen million, two hundred sixty-one thousand, eight hundred fifty-three".