215965561 has 16 divisors (see below), whose sum is σ = 265863168. Its totient is φ = 171349200.

The previous prime is 215965511. The next prime is 215965579. The reversal of 215965561 is 165569512.

It is a cyclic number.

It is not a de Polignac number, because 215965561 - 2¹³ = 215957369 is a prime.

It is a super-2 number, since 2×215965561² = 93282247076089442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (215965511) 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, 16645 + ... + 26626.

It is an arithmetic number, because the mean of its divisors is an integer number (16616448).

Almost surely, 2^215965561 is an apocalyptic number.

It is an amenable number.

215965561 is a deficient number, since it is larger than the sum of its proper divisors (49897607).

215965561 is a wasteful number, since it uses less digits than its factorization.

215965561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43332.

The product of its digits is 81000, while the sum is 40.

The square root of 215965561 is about 14695.7667714209. The cubic root of 215965561 is about 599.9681103421.

The spelling of 215965561 in words is "two hundred fifteen million, nine hundred sixty-five thousand, five hundred sixty-one".