2156615312221 has 4 divisors (see below), whose sum is σ = 2230981357500. Its totient is φ = 2082249266944.

The previous prime is 2156615312209. The next prime is 2156615312333. The reversal of 2156615312221 is 1222135166512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1068639062500 + 1087976249721 = 1033750^2 + 1043061^2 .

It is a cyclic number.

It is not a de Polignac number, because 2156615312221 - 2²¹ = 2156613215069 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 (2156615312521) 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 3 ways as a sum of consecutive naturals, for example, 37183022596 + ... + 37183022653.

It is an arithmetic number, because the mean of its divisors is an integer number (557745339375).

Almost surely, 2^{2156615312221} is an apocalyptic number.

It is an amenable number.

2156615312221 is a deficient number, since it is larger than the sum of its proper divisors (74366045279).

2156615312221 is an equidigital number, since it uses as much as digits as its factorization.

2156615312221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74366045278.

The product of its digits is 43200, while the sum is 37.

The spelling of 2156615312221 in words is "two trillion, one hundred fifty-six billion, six hundred fifteen million, three hundred twelve thousand, two hundred twenty-one".