21321723 has 8 divisors (see below), whose sum is σ = 30101328. Its totient is φ = 13378304.

The previous prime is 21321709. The next prime is 21321733. The reversal of 21321723 is 32712312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21321723 - 2¹² = 21317627 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21321723.

It is not an unprimeable number, because it can be changed into a prime (21321733) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 208986 + ... + 209087.

It is an arithmetic number, because the mean of its divisors is an integer number (3762666).

It is a self-describing number.

Almost surely, 2^21321723 is an apocalyptic number.

21321723 is a deficient number, since it is larger than the sum of its proper divisors (8779605).

21321723 is a wasteful number, since it uses less digits than its factorization.

21321723 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 418093.

The product of its digits is 504, while the sum is 21.

The square root of 21321723 is about 4617.5451270128. The cubic root of 21321723 is about 277.2941871381.

The spelling of 21321723 in words is "twenty-one million, three hundred twenty-one thousand, seven hundred twenty-three".