20990881 has 4 divisors (see below), whose sum is σ = 21903552. Its totient is φ = 20078212.

The previous prime is 20990863. The next prime is 20990891. The reversal of 20990881 is 18809902.

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 20990881 - 2¹¹ = 20988833 is a prime.

It is a super-2 number, since 2×20990881² = 881234170312322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20990881.

It is not an unprimeable number, because it can be changed into a prime (20990821) 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, 456301 + ... + 456346.

It is an arithmetic number, because the mean of its divisors is an integer number (5475888).

Almost surely, 2^20990881 is an apocalyptic number.

It is an amenable number.

20990881 is a deficient number, since it is larger than the sum of its proper divisors (912671).

20990881 is an equidigital number, since it uses as much as digits as its factorization.

20990881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 912670.

The product of its (nonzero) digits is 10368, while the sum is 37.

The square root of 20990881 is about 4581.5806224490. The cubic root of 20990881 is about 275.8524775237.

The spelling of 20990881 in words is "twenty million, nine hundred ninety thousand, eight hundred eighty-one".