66872821 has 4 divisors (see below), whose sum is σ = 66896992. Its totient is φ = 66848652.

The previous prime is 66872791. The next prime is 66872831. The reversal of 66872821 is 12827866.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66872821 - 2⁷ = 66872693 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 (66872831) 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, 7305 + ... + 13678.

It is an arithmetic number, because the mean of its divisors is an integer number (16724248).

Almost surely, 2^66872821 is an apocalyptic number.

It is an amenable number.

66872821 is a deficient number, since it is larger than the sum of its proper divisors (24171).

66872821 is a wasteful number, since it uses less digits than its factorization.

66872821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24170.

The product of its digits is 64512, while the sum is 40.

The square root of 66872821 is about 8177.5803878653. The cubic root of 66872821 is about 405.8976603907.

The spelling of 66872821 in words is "sixty-six million, eight hundred seventy-two thousand, eight hundred twenty-one".