215721161 has 4 divisors (see below), whose sum is σ = 216624000. Its totient is φ = 214818324.

The previous prime is 215721151. The next prime is 215721179. The reversal of 215721161 is 161127512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 215721161 - 2²⁶ = 148612297 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 215721161.

It is not an unprimeable number, because it can be changed into a prime (215721151) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 451061 + ... + 451538.

It is an arithmetic number, because the mean of its divisors is an integer number (54156000).

Almost surely, 2^215721161 is an apocalyptic number.

It is an amenable number.

215721161 is a deficient number, since it is larger than the sum of its proper divisors (902839).

215721161 is an equidigital number, since it uses as much as digits as its factorization.

215721161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 902838.

The product of its digits is 840, while the sum is 26.

The square root of 215721161 is about 14687.4490977841. The cubic root of 215721161 is about 599.7417045625.

Adding to 215721161 its reverse (161127512), we get a palindrome (376848673).

The spelling of 215721161 in words is "two hundred fifteen million, seven hundred twenty-one thousand, one hundred sixty-one".