66723921 has 12 divisors (see below), whose sum is σ = 105140880. Its totient is φ = 40438680.

The previous prime is 66723911. The next prime is 66723941. The reversal of 66723921 is 12932766.

It is not a de Polignac number, because 66723921 - 2⁶ = 66723857 is a prime.

It is a super-2 number, since 2×66723921² = 8904163267228482, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (66723911) 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, 336891 + ... + 337088.

It is an arithmetic number, because the mean of its divisors is an integer number (8761740).

Almost surely, 2^66723921 is an apocalyptic number.

It is an amenable number.

66723921 is a deficient number, since it is larger than the sum of its proper divisors (38416959).

66723921 is a wasteful number, since it uses less digits than its factorization.

66723921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 673996 (or 673993 counting only the distinct ones).

The product of its digits is 27216, while the sum is 36.

The square root of 66723921 is about 8168.4711543838. The cubic root of 66723921 is about 405.5961772979.

The spelling of 66723921 in words is "sixty-six million, seven hundred twenty-three thousand, nine hundred twenty-one".