21621603 has 16 divisors (see below), whose sum is σ = 30636576. Its totient is φ = 13516800.

The previous prime is 21621577. The next prime is 21621629. The reversal of 21621603 is 30612612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21621577) and next prime (21621629).

It is not a de Polignac number, because 21621603 - 2⁹ = 21621091 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21621603.

It is not an unprimeable number, because it can be changed into a prime (21621643) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17403 + ... + 18603.

It is an arithmetic number, because the mean of its divisors is an integer number (1914786).

Almost surely, 2^21621603 is an apocalyptic number.

21621603 is a deficient number, since it is larger than the sum of its proper divisors (9014973).

21621603 is a wasteful number, since it uses less digits than its factorization.

21621603 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1574.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 21621603 is about 4649.9035473868. The cubic root of 21621603 is about 278.5881437514.

The spelling of 21621603 in words is "twenty-one million, six hundred twenty-one thousand, six hundred three".