215886738839661 has 12 divisors (see below), whose sum is σ = 312106857109788. Its totient is φ = 143799666453504.

The previous prime is 215886738839657. The next prime is 215886738839687. The reversal of 215886738839661 is 166938837688512.

215886738839661 is a `hidden beast` number, since 2 + 1 + 5 + 8 + 86 + 73 + 88 + 396 + 6 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 120443491355625 + 95443247484036 = 10974675^2 + 9769506^2 .

It is not a de Polignac number, because 215886738839661 - 2² = 215886738839657 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (215886738839621) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10402164570 + ... + 10402185323.

It is an arithmetic number, because the mean of its divisors is an integer number (26008904759149).

Almost surely, 2^{215886738839661} is an apocalyptic number.

It is an amenable number.

215886738839661 is a deficient number, since it is larger than the sum of its proper divisors (96220118270127).

215886738839661 is a wasteful number, since it uses less digits than its factorization.

215886738839661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20804351052 (or 20804351049 counting only the distinct ones).

The product of its digits is 5016453120, while the sum is 81.

The spelling of 215886738839661 in words is "two hundred fifteen trillion, eight hundred eighty-six billion, seven hundred thirty-eight million, eight hundred thirty-nine thousand, six hundred sixty-one".