215690581 has 2 divisors, whose sum is σ = 215690582. Its totient is φ = 215690580.

The previous prime is 215690561. The next prime is 215690599. The reversal of 215690581 is 185096512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 190026225 + 25664356 = 13785^2 + 5066^2 .

It is a cyclic number.

It is not a de Polignac number, because 215690581 - 2¹¹ = 215688533 is a prime.

It is a super-2 number, since 2×215690581² = 93044853464235122, which contains 22 as substring.

It is equal to p_11898271 and since 215690581 and 11898271 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 215690581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215690551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107845290 + 107845291.

It is an arithmetic number, because the mean of its divisors is an integer number (107845291).

Almost surely, 2^215690581 is an apocalyptic number.

215690581 is the 9289-th centered pentagonal number.

It is an amenable number.

215690581 is a deficient number, since it is larger than the sum of its proper divisors (1).

215690581 is an equidigital number, since it uses as much as digits as its factorization.

215690581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 21600, while the sum is 37.

The square root of 215690581 is about 14686.4080360039. The cubic root of 215690581 is about 599.7133640141.

The spelling of 215690581 in words is "two hundred fifteen million, six hundred ninety thousand, five hundred eighty-one".