21740457 has 4 divisors (see below), whose sum is σ = 28987280. Its totient is φ = 14493636.

The previous prime is 21740449. The next prime is 21740479. The reversal of 21740457 is 75404712.

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 not a de Polignac number, because 21740457 - 2³ = 21740449 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21740417) 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, 3623407 + ... + 3623412.

It is an arithmetic number, because the mean of its divisors is an integer number (7246820).

Almost surely, 2^21740457 is an apocalyptic number.

It is an amenable number.

21740457 is a deficient number, since it is larger than the sum of its proper divisors (7246823).

21740457 is an equidigital number, since it uses as much as digits as its factorization.

21740457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7246822.

The product of its (nonzero) digits is 7840, while the sum is 30.

The square root of 21740457 is about 4662.6662973024. Note that the first 3 decimals coincide. The cubic root of 21740457 is about 279.0976778017.

The spelling of 21740457 in words is "twenty-one million, seven hundred forty thousand, four hundred fifty-seven".