21457789 has 4 divisors (see below), whose sum is σ = 21517920. Its totient is φ = 21397660.

The previous prime is 21457771. The next prime is 21457819. The reversal of 21457789 is 98775412.

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 21457789 - 2¹⁵ = 21425021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21457759) 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, 29527 + ... + 30244.

It is an arithmetic number, because the mean of its divisors is an integer number (5379480).

Almost surely, 2^21457789 is an apocalyptic number.

It is an amenable number.

21457789 is a deficient number, since it is larger than the sum of its proper divisors (60131).

21457789 is an equidigital number, since it uses as much as digits as its factorization.

21457789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60130.

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

The square root of 21457789 is about 4632.2552822572. The cubic root of 21457789 is about 277.8827939579.

The spelling of 21457789 in words is "twenty-one million, four hundred fifty-seven thousand, seven hundred eighty-nine".