20797981 has 2 divisors, whose sum is σ = 20797982. Its totient is φ = 20797980.

The previous prime is 20797961. The next prime is 20797999. The reversal of 20797981 is 18979702.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20702500 + 95481 = 4550^2 + 309^2 .

It is a cyclic number.

It is not a de Polignac number, because 20797981 - 2⁵ = 20797949 is a prime.

It is a super-2 number, since 2×20797981² = 865112027352722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20797921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10398990 + 10398991.

It is an arithmetic number, because the mean of its divisors is an integer number (10398991).

Almost surely, 2^20797981 is an apocalyptic number.

It is an amenable number.

20797981 is a deficient number, since it is larger than the sum of its proper divisors (1).

20797981 is an equidigital number, since it uses as much as digits as its factorization.

20797981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 20797981 is about 4560.4803475073. The cubic root of 20797981 is about 275.0048748447.

The spelling of 20797981 in words is "twenty million, seven hundred ninety-seven thousand, nine hundred eighty-one".