2156811521 has 8 divisors (see below), whose sum is σ = 2211511464. Its totient is φ = 2102630400.

The previous prime is 2156811509. The next prime is 2156811541. The reversal of 2156811521 is 1251186512.

It can be written as a sum of positive squares in 4 ways, for example, as 191130625 + 1965680896 = 13825^2 + 44336^2 .

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 2156811521 - 2¹⁸ = 2156549377 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2156811541) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 121280 + ... + 137921.

It is an arithmetic number, because the mean of its divisors is an integer number (276438933).

Almost surely, 2^2156811521 is an apocalyptic number.

It is an amenable number.

2156811521 is a deficient number, since it is larger than the sum of its proper divisors (54699943).

2156811521 is a wasteful number, since it uses less digits than its factorization.

2156811521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259411.

The product of its digits is 4800, while the sum is 32.

The square root of 2156811521 is about 46441.4849138139. The cubic root of 2156811521 is about 1292.0244480368.

The spelling of 2156811521 in words is "two billion, one hundred fifty-six million, eight hundred eleven thousand, five hundred twenty-one".