21609403 has 4 divisors (see below), whose sum is σ = 22746760. Its totient is φ = 20472048.

The previous prime is 21609391. The next prime is 21609407. The reversal of 21609403 is 30490612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21609403 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (21609407) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 568650 + ... + 568687.

It is an arithmetic number, because the mean of its divisors is an integer number (5686690).

Almost surely, 2^21609403 is an apocalyptic number.

21609403 is a deficient number, since it is larger than the sum of its proper divisors (1137357).

21609403 is a wasteful number, since it uses less digits than its factorization.

21609403 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1137356.

The product of its (nonzero) digits is 1296, while the sum is 25.

The square root of 21609403 is about 4648.5915071127. The cubic root of 21609403 is about 278.5357360613.

The spelling of 21609403 in words is "twenty-one million, six hundred nine thousand, four hundred three".