64621521 has 6 divisors (see below), whose sum is σ = 93342210. Its totient is φ = 43081008.

The previous prime is 64621511. The next prime is 64621523. The reversal of 64621521 is 12512646.

64621521 is a `hidden beast` number, since 646 + 2 + 15 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 55711296 + 8910225 = 7464^2 + 2985^2 .

It is not a de Polignac number, because 64621521 - 2⁶ = 64621457 is a prime.

It is not an unprimeable number, because it can be changed into a prime (64621523) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3590076 + ... + 3590093.

It is an arithmetic number, because the mean of its divisors is an integer number (15557035).

Almost surely, 2^64621521 is an apocalyptic number.

It is an amenable number.

64621521 is a deficient number, since it is larger than the sum of its proper divisors (28720689).

64621521 is a wasteful number, since it uses less digits than its factorization.

64621521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7180175 (or 7180172 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 64621521 is about 8038.7512089876. The cubic root of 64621521 is about 401.2906663881.

The spelling of 64621521 in words is "sixty-four million, six hundred twenty-one thousand, five hundred twenty-one".