215637661 has 2 divisors, whose sum is σ = 215637662. Its totient is φ = 215637660.

The previous prime is 215637629. The next prime is 215637679. The reversal of 215637661 is 166736512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 214183225 + 1454436 = 14635^2 + 1206^2 .

It is a cyclic number.

It is not a de Polignac number, because 215637661 - 2⁵ = 215637629 is a prime.

It is equal to p_11895526 and since 215637661 and 11895526 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 215637661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215637161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107818830 + 107818831.

It is an arithmetic number, because the mean of its divisors is an integer number (107818831).

Almost surely, 2^215637661 is an apocalyptic number.

It is an amenable number.

215637661 is a deficient number, since it is larger than the sum of its proper divisors (1).

215637661 is an equidigital number, since it uses as much as digits as its factorization.

215637661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 45360, while the sum is 37.

The square root of 215637661 is about 14684.6062596176. The cubic root of 215637661 is about 599.6643131515.

The spelling of 215637661 in words is "two hundred fifteen million, six hundred thirty-seven thousand, six hundred sixty-one".