21499621 has 32 divisors (see below), whose sum is σ = 27377280. Its totient is φ = 16588800.

The previous prime is 21499619. The next prime is 21499631. The reversal of 21499621 is 12699412.

It is a 7-Lehmer number, since φ(21499621) divides (21499621-1)⁷.

It is a cyclic number.

It is not a de Polignac number, because 21499621 - 2¹ = 21499619 is a prime.

It is a Smith number, since the sum of its digits (34) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21499631) 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 31 ways as a sum of consecutive naturals, for example, 111301 + ... + 111493.

It is an arithmetic number, because the mean of its divisors is an integer number (855540).

Almost surely, 2^21499621 is an apocalyptic number.

It is an amenable number.

21499621 is a deficient number, since it is larger than the sum of its proper divisors (5877659).

21499621 is a wasteful number, since it uses less digits than its factorization.

21499621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 277.

The product of its digits is 7776, while the sum is 34.

The square root of 21499621 is about 4636.7683789467. The cubic root of 21499621 is about 278.0632544158.

The spelling of 21499621 in words is "twenty-one million, four hundred ninety-nine thousand, six hundred twenty-one".