21865989 has 8 divisors (see below), whose sum is σ = 29323872. Its totient is φ = 14492720.

The previous prime is 21865981. The next prime is 21865993. The reversal of 21865989 is 98956812.

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 21865989 - 2³ = 21865981 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21865981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20547 + ... + 21584.

It is an arithmetic number, because the mean of its divisors is an integer number (3665484).

Almost surely, 2^21865989 is an apocalyptic number.

It is an amenable number.

21865989 is a deficient number, since it is larger than the sum of its proper divisors (7457883).

21865989 is a wasteful number, since it uses less digits than its factorization.

21865989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42307.

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

The square root of 21865989 is about 4676.1083178216. The cubic root of 21865989 is about 279.6338283183.

The spelling of 21865989 in words is "twenty-one million, eight hundred sixty-five thousand, nine hundred eighty-nine".