21789457 has 4 divisors (see below), whose sum is σ = 21833280. Its totient is φ = 21745636.

The previous prime is 21789421. The next prime is 21789463. The reversal of 21789457 is 75498712.

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 21789457 - 2⁷ = 21789329 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21789407) 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, 21157 + ... + 22162.

It is an arithmetic number, because the mean of its divisors is an integer number (5458320).

Almost surely, 2^21789457 is an apocalyptic number.

It is an amenable number.

21789457 is a deficient number, since it is larger than the sum of its proper divisors (43823).

21789457 is an equidigital number, since it uses as much as digits as its factorization.

21789457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43822.

The product of its digits is 141120, while the sum is 43.

The square root of 21789457 is about 4667.9178441785. The cubic root of 21789457 is about 279.3072030601.

The spelling of 21789457 in words is "twenty-one million, seven hundred eighty-nine thousand, four hundred fifty-seven".