66861921 has 12 divisors (see below), whose sum is σ = 103704432. Its totient is φ = 38206728.

The previous prime is 66861911. The next prime is 66861929. The reversal of 66861921 is 12916866.

It is not a de Polignac number, because 66861921 - 2⁹ = 66861409 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 66861921.

It is not an unprimeable number, because it can be changed into a prime (66861929) 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, 227275 + ... + 227568.

It is an arithmetic number, because the mean of its divisors is an integer number (8642036).

Almost surely, 2^66861921 is an apocalyptic number.

It is an amenable number.

66861921 is a deficient number, since it is larger than the sum of its proper divisors (36842511).

66861921 is a wasteful number, since it uses less digits than its factorization.

66861921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 454860 (or 454853 counting only the distinct ones).

The product of its digits is 31104, while the sum is 39.

The square root of 66861921 is about 8176.9139044018. The cubic root of 66861921 is about 405.8756059654.

The spelling of 66861921 in words is "sixty-six million, eight hundred sixty-one thousand, nine hundred twenty-one".