20999989 has 8 divisors (see below), whose sum is σ = 22620672. Its totient is φ = 19438320.

The previous prime is 20999977. The next prime is 20999999. The reversal of 20999989 is 98999902.

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 20999989 - 2⁹ = 20999477 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 (20999939) 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, 14014 + ... + 15439.

It is an arithmetic number, because the mean of its divisors is an integer number (2827584).

Almost surely, 2^20999989 is an apocalyptic number.

It is an amenable number.

20999989 is a deficient number, since it is larger than the sum of its proper divisors (1620683).

20999989 is a wasteful number, since it uses less digits than its factorization.

20999989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29507.

The product of its (nonzero) digits is 944784, while the sum is 55.

The square root of 20999989 is about 4582.5744947573. The cubic root of 20999989 is about 275.8923694664.

The spelling of 20999989 in words is "twenty million, nine hundred ninety-nine thousand, nine hundred eighty-nine".