21723457 has 8 divisors (see below), whose sum is σ = 24856832. Its totient is φ = 18597600.

The previous prime is 21723451. The next prime is 21723463. The reversal of 21723457 is 75432712.

It is an interprime number because it is at equal distance from previous prime (21723451) and next prime (21723463).

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

It is not a de Polignac number, because 21723457 - 2¹¹ = 21721409 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21723451) 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, 7357 + ... + 9877.

It is an arithmetic number, because the mean of its divisors is an integer number (3107104).

Almost surely, 2^21723457 is an apocalyptic number.

It is an amenable number.

21723457 is a deficient number, since it is larger than the sum of its proper divisors (3133375).

21723457 is a wasteful number, since it uses less digits than its factorization.

21723457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3759.

The product of its digits is 11760, while the sum is 31.

The square root of 21723457 is about 4660.8429495103. The cubic root of 21723457 is about 279.0249118097.

The spelling of 21723457 in words is "twenty-one million, seven hundred twenty-three thousand, four hundred fifty-seven".