215661361 has 8 divisors (see below), whose sum is σ = 220051944. Its totient is φ = 211315200.

The previous prime is 215661359. The next prime is 215661373. The reversal of 215661361 is 163166512.

It can be written as a sum of positive squares in 4 ways, for example, as 102111025 + 113550336 = 10105^2 + 10656^2 .

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 215661361 - 2¹ = 215661359 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (215661331) 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, 1210 + ... + 20803.

It is an arithmetic number, because the mean of its divisors is an integer number (27506493).

Almost surely, 2^215661361 is an apocalyptic number.

It is an amenable number.

215661361 is a deficient number, since it is larger than the sum of its proper divisors (4390583).

215661361 is a wasteful number, since it uses less digits than its factorization.

215661361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22211.

The product of its digits is 6480, while the sum is 31.

The square root of 215661361 is about 14685.4132049459. The cubic root of 215661361 is about 599.6862813667.

The spelling of 215661361 in words is "two hundred fifteen million, six hundred sixty-one thousand, three hundred sixty-one".