66561157 has 6 divisors (see below), whose sum is σ = 72075282. Its totient is φ = 61440912.

The previous prime is 66561133. The next prime is 66561197. The reversal of 66561157 is 75116566.

It can be written as a sum of positive squares in 3 ways, for example, as 73441 + 66487716 = 271^2 + 8154^2 .

It is not a de Polignac number, because 66561157 - 2⁷ = 66561029 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66561127) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 196758 + ... + 197095.

It is an arithmetic number, because the mean of its divisors is an integer number (12012547).

Almost surely, 2^66561157 is an apocalyptic number.

It is an amenable number.

66561157 is a deficient number, since it is larger than the sum of its proper divisors (5514125).

66561157 is a wasteful number, since it uses less digits than its factorization.

66561157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 393879 (or 393866 counting only the distinct ones).

The product of its digits is 37800, while the sum is 37.

The square root of 66561157 is about 8158.5021296804. The cubic root of 66561157 is about 405.2661097225.

The spelling of 66561157 in words is "sixty-six million, five hundred sixty-one thousand, one hundred fifty-seven".