21750621 has 8 divisors (see below), whose sum is σ = 29327040. Its totient is φ = 14337312.

The previous prime is 21750563. The next prime is 21750629. The reversal of 21750621 is 12605712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21750621 - 2⁹ = 21750109 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21750591 and 21750600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21750629) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40465 + ... + 40998.

It is an arithmetic number, because the mean of its divisors is an integer number (3665880).

Almost surely, 2^21750621 is an apocalyptic number.

It is an amenable number.

21750621 is a deficient number, since it is larger than the sum of its proper divisors (7576419).

21750621 is an equidigital number, since it uses as much as digits as its factorization.

21750621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81555.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21750621 is about 4663.7561042576. The cubic root of 21750621 is about 279.1411651862.

The spelling of 21750621 in words is "twenty-one million, seven hundred fifty thousand, six hundred twenty-one".