21499989 has 16 divisors (see below), whose sum is σ = 32934528. Its totient is φ = 12220992.

The previous prime is 21499981. The next prime is 21500021. The reversal of 21499989 is 98999412.

It is a happy number.

It is not a de Polignac number, because 21499989 - 2³ = 21499981 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21499981) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1539 + ... + 6735.

It is an arithmetic number, because the mean of its divisors is an integer number (2058408).

Almost surely, 2^21499989 is an apocalyptic number.

It is an amenable number.

21499989 is a deficient number, since it is larger than the sum of its proper divisors (11434539).

21499989 is a wasteful number, since it uses less digits than its factorization.

21499989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5404.

The product of its digits is 419904, while the sum is 51.

The square root of 21499989 is about 4636.8080615872. The cubic root of 21499989 is about 278.0648409041.

The spelling of 21499989 in words is "twenty-one million, four hundred ninety-nine thousand, nine hundred eighty-nine".