215531761 has 9 divisors (see below), whose sum is σ = 220471041. Its totient is φ = 210701712.

The previous prime is 215531759. The next prime is 215531773. The reversal of 215531761 is 167135512.

The square root of 215531761 is 14681.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 3538161 + 211993600 = 1881^2 + 14560^2 .

It is not a de Polignac number, because 215531761 - 2¹ = 215531759 is a prime.

It is a super-2 number, since 2×215531761² = 92907879999522242, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (215532761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 777955 + ... + 778231.

Almost surely, 2^215531761 is an apocalyptic number.

215531761 is the 14681-st square number.

215531761 is the 7341-st centered octagonal number.

It is an amenable number.

215531761 is a deficient number, since it is larger than the sum of its proper divisors (4939280).

215531761 is an frugal number, since it uses more digits than its factorization.

215531761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 660 (or 330 counting only the distinct ones).

The product of its digits is 6300, while the sum is 31.

The cubic root of 215531761 is about 599.5661317098.

The spelling of 215531761 in words is "two hundred fifteen million, five hundred thirty-one thousand, seven hundred sixty-one".