66503921 has 4 divisors (see below), whose sum is σ = 72549744. Its totient is φ = 60458100.

The previous prime is 66503903. The next prime is 66503947. The reversal of 66503921 is 12930566.

It is a happy number.

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 66503921 - 2²² = 62309617 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66503951) 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, 3022895 + ... + 3022916.

It is an arithmetic number, because the mean of its divisors is an integer number (18137436).

Almost surely, 2^66503921 is an apocalyptic number.

It is an amenable number.

66503921 is a deficient number, since it is larger than the sum of its proper divisors (6045823).

66503921 is a wasteful number, since it uses less digits than its factorization.

66503921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6045822.

The product of its (nonzero) digits is 9720, while the sum is 32.

The square root of 66503921 is about 8154.9936235413. The cubic root of 66503921 is about 405.1499135104.

The spelling of 66503921 in words is "sixty-six million, five hundred three thousand, nine hundred twenty-one".