61866991521 has 12 divisors (see below), whose sum is σ = 89541099648. Its totient is φ = 41162660664.

The previous prime is 61866991519. The next prime is 61866991567. The reversal of 61866991521 is 12519966816.

61866991521 is a `hidden beast` number, since 618 + 6 + 6 + 9 + 9 + 15 + 2 + 1 = 666.

It is not a de Polignac number, because 61866991521 - 2¹ = 61866991519 is a prime.

It is not an unprimeable number, because it can be changed into a prime (61866991591) 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, 6828585 + ... + 6837638.

It is an arithmetic number, because the mean of its divisors is an integer number (7461758304).

Almost surely, 2^61866991521 is an apocalyptic number.

It is an amenable number.

61866991521 is a deficient number, since it is larger than the sum of its proper divisors (27674108127).

61866991521 is a wasteful number, since it uses less digits than its factorization.

61866991521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13666732 (or 13666729 counting only the distinct ones).

The product of its digits is 1399680, while the sum is 54.

The spelling of 61866991521 in words is "sixty-one billion, eight hundred sixty-six million, nine hundred ninety-one thousand, five hundred twenty-one".