21266621 has 8 divisors (see below), whose sum is σ = 21821400. Its totient is φ = 20717632.

The previous prime is 21266617. The next prime is 21266629. The reversal of 21266621 is 12666212.

It can be written as a sum of positive squares in 4 ways, for example, as 1240996 + 20025625 = 1114^2 + 4475^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21266621 - 2² = 21266617 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 (21266629) 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, 6551 + ... + 9243.

It is an arithmetic number, because the mean of its divisors is an integer number (2727675).

Almost surely, 2^21266621 is an apocalyptic number.

It is an amenable number.

21266621 is a deficient number, since it is larger than the sum of its proper divisors (554779).

21266621 is a wasteful number, since it uses less digits than its factorization.

21266621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2895.

The product of its digits is 1728, while the sum is 26.

The square root of 21266621 is about 4611.5746768322. The cubic root of 21266621 is about 277.0551094373.

The spelling of 21266621 in words is "twenty-one million, two hundred sixty-six thousand, six hundred twenty-one".