20899981 has 16 divisors (see below), whose sum is σ = 23083200. Its totient is φ = 18845568.

The previous prime is 20899979. The next prime is 20899993. The reversal of 20899981 is 18999802.

It is a happy number.

It is not a de Polignac number, because 20899981 - 2¹ = 20899979 is a prime.

It is a super-2 number, since 2×20899981² = 873618411600722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20899951) 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, 45505 + ... + 45961.

It is an arithmetic number, because the mean of its divisors is an integer number (1442700).

Almost surely, 2^20899981 is an apocalyptic number.

It is an amenable number.

20899981 is a deficient number, since it is larger than the sum of its proper divisors (2183219).

20899981 is a wasteful number, since it uses less digits than its factorization.

20899981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 588.

The product of its (nonzero) digits is 93312, while the sum is 46.

The square root of 20899981 is about 4571.6497022410. The cubic root of 20899981 is about 275.4537127318.

The spelling of 20899981 in words is "twenty million, eight hundred ninety-nine thousand, nine hundred eighty-one".