21660501 has 4 divisors (see below), whose sum is σ = 28880672. Its totient is φ = 14440332.

The previous prime is 21660491. The next prime is 21660521. The reversal of 21660501 is 10506612.

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 21660501 - 2⁵ = 21660469 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 (21660521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3610081 + ... + 3610086.

It is an arithmetic number, because the mean of its divisors is an integer number (7220168).

Almost surely, 2^21660501 is an apocalyptic number.

It is an amenable number.

21660501 is a deficient number, since it is larger than the sum of its proper divisors (7220171).

21660501 is an equidigital number, since it uses as much as digits as its factorization.

21660501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7220170.

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

The square root of 21660501 is about 4654.0843352909. The cubic root of 21660501 is about 278.7551068528.

The spelling of 21660501 in words is "twenty-one million, six hundred sixty thousand, five hundred one".