21684403 has 4 divisors (see below), whose sum is σ = 23352448. Its totient is φ = 20016360.

The previous prime is 21684371. The next prime is 21684409. The reversal of 21684403 is 30448612.

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

It is not a de Polignac number, because 21684403 - 2⁵ = 21684371 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21684409) 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, 834003 + ... + 834028.

It is an arithmetic number, because the mean of its divisors is an integer number (5838112).

Almost surely, 2^21684403 is an apocalyptic number.

21684403 is a deficient number, since it is larger than the sum of its proper divisors (1668045).

21684403 is a wasteful number, since it uses less digits than its factorization.

21684403 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1668044.

The product of its (nonzero) digits is 4608, while the sum is 28.

The square root of 21684403 is about 4656.6514793358. The cubic root of 21684403 is about 278.8576030246.

The spelling of 21684403 in words is "twenty-one million, six hundred eighty-four thousand, four hundred three".