21392473 has 4 divisors (see below), whose sum is σ = 21847680. Its totient is φ = 20937268.

The previous prime is 21392467. The next prime is 21392491. The reversal of 21392473 is 37429312.

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-21392473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21392453) 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, 227533 + ... + 227626.

It is an arithmetic number, because the mean of its divisors is an integer number (5461920).

Almost surely, 2^21392473 is an apocalyptic number.

It is an amenable number.

21392473 is a deficient number, since it is larger than the sum of its proper divisors (455207).

21392473 is an equidigital number, since it uses as much as digits as its factorization.

21392473 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 455206.

The product of its digits is 9072, while the sum is 31.

The square root of 21392473 is about 4625.1997794690. The cubic root of 21392473 is about 277.6005555014.

The spelling of 21392473 in words is "twenty-one million, three hundred ninety-two thousand, four hundred seventy-three".