20989581 has 8 divisors (see below), whose sum is σ = 28668864. Its totient is φ = 13651680.

The previous prime is 20989567. The next prime is 20989601. The reversal of 20989581 is 18598902.

It is a happy number.

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

It is not a de Polignac number, because 20989581 - 2¹⁵ = 20956813 is a prime.

It is a super-2 number, since 2×20989581² = 881125021111122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20989531) 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, 85201 + ... + 85446.

It is an arithmetic number, because the mean of its divisors is an integer number (3583608).

Almost surely, 2^20989581 is an apocalyptic number.

It is an amenable number.

20989581 is a deficient number, since it is larger than the sum of its proper divisors (7679283).

20989581 is a wasteful number, since it uses less digits than its factorization.

20989581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 170691.

The product of its (nonzero) digits is 51840, while the sum is 42.

The square root of 20989581 is about 4581.4387478171. The cubic root of 20989581 is about 275.8467827394.

The spelling of 20989581 in words is "twenty million, nine hundred eighty-nine thousand, five hundred eighty-one".