21276621 has 8 divisors (see below), whose sum is σ = 31520960. Its totient is φ = 14184396.

The previous prime is 21276613. The next prime is 21276623. The reversal of 21276621 is 12667212.

It is not a de Polignac number, because 21276621 - 2³ = 21276613 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 788023 = 21276621 / (2 + 1 + 2 + 7 + 6 + 6 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21276623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 393985 + ... + 394038.

It is an arithmetic number, because the mean of its divisors is an integer number (3940120).

Almost surely, 2^21276621 is an apocalyptic number.

It is an amenable number.

21276621 is a deficient number, since it is larger than the sum of its proper divisors (10244339).

21276621 is an equidigital number, since it uses as much as digits as its factorization.

21276621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 788032 (or 788026 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 21276621 is about 4612.6587777550. The cubic root of 21276621 is about 277.0985282915.

The spelling of 21276621 in words is "twenty-one million, two hundred seventy-six thousand, six hundred twenty-one".