215821197 has 6 divisors (see below), whose sum is σ = 311741742. Its totient is φ = 143880792.

The previous prime is 215821097. The next prime is 215821201. The reversal of 215821197 is 791128512.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 115541001 + 100280196 = 10749^2 + 10014^2 .

It is not a de Polignac number, because 215821197 - 2²² = 211626893 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (215821097) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 11990058 + ... + 11990075.

It is an arithmetic number, because the mean of its divisors is an integer number (51956957).

Almost surely, 2^215821197 is an apocalyptic number.

It is an amenable number.

215821197 is a deficient number, since it is larger than the sum of its proper divisors (95920545).

215821197 is a wasteful number, since it uses less digits than its factorization.

215821197 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23980139 (or 23980136 counting only the distinct ones).

The product of its digits is 10080, while the sum is 36.

The square root of 215821197 is about 14690.8541957233. The cubic root of 215821197 is about 599.8343959630.

The spelling of 215821197 in words is "two hundred fifteen million, eight hundred twenty-one thousand, one hundred ninety-seven".