20978681 has 2 divisors, whose sum is σ = 20978682. Its totient is φ = 20978680.

The previous prime is 20978677. The next prime is 20978701. The reversal of 20978681 is 18687902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11424400 + 9554281 = 3380^2 + 3091^2 .

It is a cyclic number.

It is not a de Polignac number, because 20978681 - 2² = 20978677 is a prime.

It is a super-2 number, since 2×20978681² = 880210112999522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20978611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10489340 + 10489341.

It is an arithmetic number, because the mean of its divisors is an integer number (10489341).

Almost surely, 2^20978681 is an apocalyptic number.

It is an amenable number.

20978681 is a deficient number, since it is larger than the sum of its proper divisors (1).

20978681 is an equidigital number, since it uses as much as digits as its factorization.

20978681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 20978681 is about 4580.2490106980. The cubic root of 20978681 is about 275.7990249089.

The spelling of 20978681 in words is "twenty million, nine hundred seventy-eight thousand, six hundred eighty-one".