20868981 has 16 divisors (see below), whose sum is σ = 33183744. Its totient is φ = 11406384.

The previous prime is 20868971. The next prime is 20868989. The reversal of 20868981 is 18986802.

It is not a de Polignac number, because 20868981 - 2⁷ = 20868853 is a prime.

It is a super-2 number, since 2×20868981² = 871028735956722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20868989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21121 + ... + 22086.

It is an arithmetic number, because the mean of its divisors is an integer number (2073984).

Almost surely, 2^20868981 is an apocalyptic number.

20868981 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20868981 is a deficient number, since it is larger than the sum of its proper divisors (12314763).

20868981 is a wasteful number, since it uses less digits than its factorization.

20868981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43240.

The product of its (nonzero) digits is 55296, while the sum is 42.

The square root of 20868981 is about 4568.2579830828. The cubic root of 20868981 is about 275.3174559820.

The spelling of 20868981 in words is "twenty million, eight hundred sixty-eight thousand, nine hundred eighty-one".