20981919 has 16 divisors (see below), whose sum is σ = 32096768. Its totient is φ = 11943072.

The previous prime is 20981899. The next prime is 20981929. The reversal of 20981919 is 91918902.

It is a happy number.

It is not a de Polignac number, because 20981919 - 2⁵ = 20981887 is a prime.

It is a super-2 number, since 2×20981919² = 880481849845122, 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 (20981929) 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, 4014 + ... + 7620.

It is an arithmetic number, because the mean of its divisors is an integer number (2006048).

Almost surely, 2^20981919 is an apocalyptic number.

20981919 is a deficient number, since it is larger than the sum of its proper divisors (11114849).

20981919 is a wasteful number, since it uses less digits than its factorization.

20981919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3894.

The product of its (nonzero) digits is 11664, while the sum is 39.

The square root of 20981919 is about 4580.6024712913. The cubic root of 20981919 is about 275.8132137784.

It can be divided in two parts, 209 and 81919, that added together give a palindrome (82128).

The spelling of 20981919 in words is "twenty million, nine hundred eighty-one thousand, nine hundred nineteen".