66564021 has 4 divisors (see below), whose sum is σ = 88752032. Its totient is φ = 44376012.

The previous prime is 66564013. The next prime is 66564023. The reversal of 66564021 is 12046566.

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 not a de Polignac number, because 66564021 - 2³ = 66564013 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 66564021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66564023) 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, 11094001 + ... + 11094006.

It is an arithmetic number, because the mean of its divisors is an integer number (22188008).

Almost surely, 2^66564021 is an apocalyptic number.

It is an amenable number.

66564021 is a deficient number, since it is larger than the sum of its proper divisors (22188011).

66564021 is a wasteful number, since it uses less digits than its factorization.

66564021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22188010.

The product of its (nonzero) digits is 8640, while the sum is 30.

The square root of 66564021 is about 8158.6776502078. The cubic root of 66564021 is about 405.2719222491.

The spelling of 66564021 in words is "sixty-six million, five hundred sixty-four thousand, twenty-one".