66501621 has 16 divisors (see below), whose sum is σ = 99024000. Its totient is φ = 44108064.

The previous prime is 66501599. The next prime is 66501623. The reversal of 66501621 is 12610566.

It is a happy number.

66501621 is a `hidden beast` number, since 6 + 650 + 1 + 6 + 2 + 1 = 666.

It is not a de Polignac number, because 66501621 - 2⁷ = 66501493 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66501623) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 816 + ... + 11561.

It is an arithmetic number, because the mean of its divisors is an integer number (6189000).

Almost surely, 2^66501621 is an apocalyptic number.

It is an amenable number.

66501621 is a deficient number, since it is larger than the sum of its proper divisors (32522379).

66501621 is a wasteful number, since it uses less digits than its factorization.

66501621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12585 (or 12579 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 66501621 is about 8154.8526044313. The cubic root of 66501621 is about 405.1452428307.

The spelling of 66501621 in words is "sixty-six million, five hundred one thousand, six hundred twenty-one".