21723993 has 6 divisors (see below), whose sum is σ = 31379114. Its totient is φ = 14482656.

The previous prime is 21723979. The next prime is 21724007. The reversal of 21723993 is 39932712.

It is an interprime number because it is at equal distance from previous prime (21723979) and next prime (21724007).

It can be written as a sum of positive squares in only one way, i.e., 14040009 + 7683984 = 3747^2 + 2772^2 .

It is not a de Polignac number, because 21723993 - 2¹⁶ = 21658457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21723913) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1206880 + ... + 1206897.

Almost surely, 2^21723993 is an apocalyptic number.

It is an amenable number.

21723993 is a deficient number, since it is larger than the sum of its proper divisors (9655121).

21723993 is a wasteful number, since it uses less digits than its factorization.

21723993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2413783 (or 2413780 counting only the distinct ones).

The product of its digits is 20412, while the sum is 36.

The square root of 21723993 is about 4660.9004494840. The cubic root of 21723993 is about 279.0272066581.

The spelling of 21723993 in words is "twenty-one million, seven hundred twenty-three thousand, nine hundred ninety-three".