66872521 has 4 divisors (see below), whose sum is σ = 69178500. Its totient is φ = 64566544.

The previous prime is 66872503. The next prime is 66872527. The reversal of 66872521 is 12527866.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 47114496 + 19758025 = 6864^2 + 4445^2 .

It is a cyclic number.

It is not a de Polignac number, because 66872521 - 2¹⁵ = 66839753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66872527) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1152946 + ... + 1153003.

It is an arithmetic number, because the mean of its divisors is an integer number (17294625).

Almost surely, 2^66872521 is an apocalyptic number.

It is an amenable number.

66872521 is a deficient number, since it is larger than the sum of its proper divisors (2305979).

66872521 is a wasteful number, since it uses less digits than its factorization.

66872521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2305978.

The product of its digits is 40320, while the sum is 37.

The square root of 66872521 is about 8177.5620450107. The cubic root of 66872521 is about 405.8970534202.

It can be divided in two parts, 668725 and 21, that added together give a triangular number (668746 = T₁₁₅₆).

The spelling of 66872521 in words is "sixty-six million, eight hundred seventy-two thousand, five hundred twenty-one".