21457989 has 36 divisors (see below), whose sum is σ = 36658336. Its totient is φ = 11841984.

The previous prime is 21457981. The next prime is 21457993. The reversal of 21457989 is 98975412.

It is not a de Polignac number, because 21457989 - 2³ = 21457981 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 (21457981) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 241057 + ... + 241145.

Almost surely, 2^21457989 is an apocalyptic number.

It is an amenable number.

21457989 is a deficient number, since it is larger than the sum of its proper divisors (15200347).

21457989 is an equidigital number, since it uses as much as digits as its factorization.

21457989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 234 (or 142 counting only the distinct ones).

The product of its digits is 181440, while the sum is 45.

The square root of 21457989 is about 4632.2768699636. The cubic root of 21457989 is about 277.8836573024.

The spelling of 21457989 in words is "twenty-one million, four hundred fifty-seven thousand, nine hundred eighty-nine".