21372473 has 4 divisors (see below), whose sum is σ = 22497360. Its totient is φ = 20247588.

The previous prime is 21372469. The next prime is 21372479. The reversal of 21372473 is 37427312.

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 not a de Polignac number, because 21372473 - 2² = 21372469 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21372479) 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, 562415 + ... + 562452.

It is an arithmetic number, because the mean of its divisors is an integer number (5624340).

Almost surely, 2^21372473 is an apocalyptic number.

It is an amenable number.

21372473 is a deficient number, since it is larger than the sum of its proper divisors (1124887).

21372473 is a wasteful number, since it uses less digits than its factorization.

21372473 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1124886.

The product of its digits is 7056, while the sum is 29.

The square root of 21372473 is about 4623.0372051282. The cubic root of 21372473 is about 277.5140181756.

Adding to 21372473 its reverse (37427312), we get a palindrome (58799785).

The spelling of 21372473 in words is "twenty-one million, three hundred seventy-two thousand, four hundred seventy-three".