215561331 has 10 divisors (see below), whose sum is σ = 322011492. Its totient is φ = 143707500.

The previous prime is 215561323. The next prime is 215561351. The reversal of 215561331 is 133165512.

215561331 is a `hidden beast` number, since 2 + 15 + 5 + 613 + 31 = 666.

It is not a de Polignac number, because 215561331 - 2³ = 215561323 is a prime.

It is a super-2 number, since 2×215561331² = 92933374844983122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 215561295 and 215561304.

It is not an unprimeable number, because it can be changed into a prime (215561351) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 1330545 + ... + 1330706.

Almost surely, 2^215561331 is an apocalyptic number.

215561331 is a deficient number, since it is larger than the sum of its proper divisors (106450161).

215561331 is an equidigital number, since it uses as much as digits as its factorization.

215561331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2661263 (or 2661254 counting only the distinct ones).

The product of its digits is 2700, while the sum is 27.

The square root of 215561331 is about 14682.0070494466. The cubic root of 215561331 is about 599.5935497258.

The spelling of 215561331 in words is "two hundred fifteen million, five hundred sixty-one thousand, three hundred thirty-one".