21658989 has 8 divisors (see below), whose sum is σ = 31504032. Its totient is φ = 13126640.

The previous prime is 21658979. The next prime is 21659017. The reversal of 21658989 is 98985612.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21658989 - 2⁵ = 21658957 is a prime.

It is a super-2 number, since 2×21658989² = 938223609004242, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21658919) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 328134 + ... + 328199.

It is an arithmetic number, because the mean of its divisors is an integer number (3938004).

Almost surely, 2^21658989 is an apocalyptic number.

It is an amenable number.

21658989 is a deficient number, since it is larger than the sum of its proper divisors (9845043).

21658989 is a wasteful number, since it uses less digits than its factorization.

21658989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 656347.

The product of its digits is 311040, while the sum is 48.

The square root of 21658989 is about 4653.9218944886. The cubic root of 21658989 is about 278.7486205834.

The spelling of 21658989 in words is "twenty-one million, six hundred fifty-eight thousand, nine hundred eighty-nine".