66173581 has 2 divisors, whose sum is σ = 66173582. Its totient is φ = 66173580.

The previous prime is 66173567. The next prime is 66173587. The reversal of 66173581 is 18537166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 65853225 + 320356 = 8115^2 + 566^2 .

It is a cyclic number.

It is not a de Polignac number, because 66173581 - 2⁷ = 66173453 is a prime.

It is a super-2 number, since 2×66173581² = 8757885644727122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 66173581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66173587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33086790 + 33086791.

It is an arithmetic number, because the mean of its divisors is an integer number (33086791).

Almost surely, 2^66173581 is an apocalyptic number.

It is an amenable number.

66173581 is a deficient number, since it is larger than the sum of its proper divisors (1).

66173581 is an equidigital number, since it uses as much as digits as its factorization.

66173581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30240, while the sum is 37.

The square root of 66173581 is about 8134.7145616795. The cubic root of 66173581 is about 404.4779760072.

The spelling of 66173581 in words is "sixty-six million, one hundred seventy-three thousand, five hundred eighty-one".