215365981 has 2 divisors, whose sum is σ = 215365982. Its totient is φ = 215365980.

The previous prime is 215365967. The next prime is 215365991. The reversal of 215365981 is 189563512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 175562500 + 39803481 = 13250^2 + 6309^2 .

It is a cyclic number.

It is not a de Polignac number, because 215365981 - 2⁷ = 215365853 is a prime.

It is a super-2 number, since 2×215365981² = 92765011544184722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215365901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107682990 + 107682991.

It is an arithmetic number, because the mean of its divisors is an integer number (107682991).

Almost surely, 2^215365981 is an apocalyptic number.

It is an amenable number.

215365981 is a deficient number, since it is larger than the sum of its proper divisors (1).

215365981 is an equidigital number, since it uses as much as digits as its factorization.

215365981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 64800, while the sum is 40.

The square root of 215365981 is about 14675.3528407327. The cubic root of 215365981 is about 599.4123700433.

The spelling of 215365981 in words is "two hundred fifteen million, three hundred sixty-five thousand, nine hundred eighty-one".