20990381 has 4 divisors (see below), whose sum is σ = 21012000. Its totient is φ = 20968764.

The previous prime is 20990353. The next prime is 20990399. The reversal of 20990381 is 18309902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20990381 - 2²² = 16796077 is a prime.

It is a super-2 number, since 2×20990381² = 881192189050322, 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 (20990311) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9281 + ... + 11318.

It is an arithmetic number, because the mean of its divisors is an integer number (5253000).

Almost surely, 2^20990381 is an apocalyptic number.

It is an amenable number.

20990381 is a deficient number, since it is larger than the sum of its proper divisors (21619).

20990381 is a wasteful number, since it uses less digits than its factorization.

20990381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21618.

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 20990381 is about 4581.5260558028. The cubic root of 20990381 is about 275.8502872499.

The spelling of 20990381 in words is "twenty million, nine hundred ninety thousand, three hundred eighty-one".