21723451 has 2 divisors, whose sum is σ = 21723452. Its totient is φ = 21723450.

The previous prime is 21723419. The next prime is 21723463. The reversal of 21723451 is 15432712.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21723451 - 2⁵ = 21723419 is a prime.

It is not a weakly prime, because it can be changed into another prime (21727451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10861725 + 10861726.

It is an arithmetic number, because the mean of its divisors is an integer number (10861726).

Almost surely, 2^21723451 is an apocalyptic number.

21723451 is a deficient number, since it is larger than the sum of its proper divisors (1).

21723451 is an equidigital number, since it uses as much as digits as its factorization.

21723451 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1680, while the sum is 25.

The square root of 21723451 is about 4660.8423058499. The cubic root of 21723451 is about 279.0248861209.

The spelling of 21723451 in words is "twenty-one million, seven hundred twenty-three thousand, four hundred fifty-one".