21923729 has 4 divisors (see below), whose sum is σ = 21940800. Its totient is φ = 21906660.

The previous prime is 21923723. The next prime is 21923731. The reversal of 21923729 is 92732912.

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 21923729 - 2¹² = 21919633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21923723) 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, 6437 + ... + 9234.

It is an arithmetic number, because the mean of its divisors is an integer number (5485200).

Almost surely, 2^21923729 is an apocalyptic number.

It is an amenable number.

21923729 is a deficient number, since it is larger than the sum of its proper divisors (17071).

21923729 is a wasteful number, since it uses less digits than its factorization.

21923729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17070.

The product of its digits is 13608, while the sum is 35.

The square root of 21923729 is about 4682.2781848156. The cubic root of 21923729 is about 279.8797485331.

The spelling of 21923729 in words is "twenty-one million, nine hundred twenty-three thousand, seven hundred twenty-nine".