66501021 has 4 divisors (see below), whose sum is σ = 88668032. Its totient is φ = 44334012.

The previous prime is 66500939. The next prime is 66501049. The reversal of 66501021 is 12010566.

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 not a de Polignac number, because 66501021 - 2¹¹ = 66498973 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66506021) 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, 11083501 + ... + 11083506.

It is an arithmetic number, because the mean of its divisors is an integer number (22167008).

Almost surely, 2^66501021 is an apocalyptic number.

It is an amenable number.

66501021 is a deficient number, since it is larger than the sum of its proper divisors (22167011).

66501021 is a wasteful number, since it uses less digits than its factorization.

66501021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22167010.

The product of its (nonzero) digits is 360, while the sum is 21.

The square root of 66501021 is about 8154.8158164363. The cubic root of 66501021 is about 405.1440243748.

Adding to 66501021 its reverse (12010566), we get a palindrome (78511587).

The spelling of 66501021 in words is "sixty-six million, five hundred one thousand, twenty-one".