21640403 has 4 divisors (see below), whose sum is σ = 21850608. Its totient is φ = 21430200.

The previous prime is 21640379. The next prime is 21640427. The reversal of 21640403 is 30404612.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (21640379) and next prime (21640427).

It is a cyclic number.

It is not a de Polignac number, because 21640403 - 2⁸ = 21640147 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21642403) 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, 104948 + ... + 105153.

It is an arithmetic number, because the mean of its divisors is an integer number (5462652).

Almost surely, 2^21640403 is an apocalyptic number.

21640403 is a deficient number, since it is larger than the sum of its proper divisors (210205).

21640403 is a wasteful number, since it uses less digits than its factorization.

21640403 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210204.

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 21640403 is about 4651.9246554518. The cubic root of 21640403 is about 278.6688645602.

The spelling of 21640403 in words is "twenty-one million, six hundred forty thousand, four hundred three".