20909881 has 4 divisors (see below), whose sum is σ = 22139892. Its totient is φ = 19679872.

The previous prime is 20909869. The next prime is 20909893. The reversal of 20909881 is 18890902.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (20909869) and next prime (20909893).

It can be written as a sum of positive squares in 2 ways, for example, as 17505856 + 3404025 = 4184^2 + 1845^2 .

It is a cyclic number.

It is not a de Polignac number, because 20909881 - 2⁷ = 20909753 is a prime.

It is a super-2 number, since 2×20909881² = 874446246868322, 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 20909881.

It is not an unprimeable number, because it can be changed into a prime (20909821) 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, 614980 + ... + 615013.

It is an arithmetic number, because the mean of its divisors is an integer number (5534973).

Almost surely, 2^20909881 is an apocalyptic number.

It is an amenable number.

20909881 is a deficient number, since it is larger than the sum of its proper divisors (1230011).

20909881 is a wasteful number, since it uses less digits than its factorization.

20909881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1230010.

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

The square root of 20909881 is about 4572.7323341740. The cubic root of 20909881 is about 275.4971985973.

The spelling of 20909881 in words is "twenty million, nine hundred nine thousand, eight hundred eighty-one".