215999989 has 2 divisors, whose sum is σ = 215999990. Its totient is φ = 215999988.

The previous prime is 215999933. The next prime is 216000007. The reversal of 215999989 is 989999512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 212197489 + 3802500 = 14567^2 + 1950^2 .

It is a cyclic number.

It is not a de Polignac number, because 215999989 - 2⁹ = 215999477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215999389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107999994 + 107999995.

It is an arithmetic number, because the mean of its divisors is an integer number (107999995).

Almost surely, 2^215999989 is an apocalyptic number.

It is an amenable number.

215999989 is a deficient number, since it is larger than the sum of its proper divisors (1).

215999989 is an equidigital number, since it uses as much as digits as its factorization.

215999989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4723920, while the sum is 61.

The square root of 215999989 is about 14696.9380824715. The cubic root of 215999989 is about 599.9999898148. Note that the first 4 decimals are identical.

The spelling of 215999989 in words is "two hundred fifteen million, nine hundred ninety-nine thousand, nine hundred eighty-nine".