21403873 has 4 divisors (see below), whose sum is σ = 21705408. Its totient is φ = 21102340.

The previous prime is 21403849. The next prime is 21403883. The reversal of 21403873 is 37830412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21403873 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21403813) 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 3 ways as a sum of consecutive naturals, for example, 150661 + ... + 150802.

It is an arithmetic number, because the mean of its divisors is an integer number (5426352).

Almost surely, 2^21403873 is an apocalyptic number.

It is an amenable number.

21403873 is a deficient number, since it is larger than the sum of its proper divisors (301535).

21403873 is an equidigital number, since it uses as much as digits as its factorization.

21403873 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 301534.

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 21403873 is about 4626.4319945288. The cubic root of 21403873 is about 277.6498576454.

The spelling of 21403873 in words is "twenty-one million, four hundred three thousand, eight hundred seventy-three".