20997761 has 2 divisors, whose sum is σ = 20997762. Its totient is φ = 20997760.

The previous prime is 20997731. The next prime is 20997829. The reversal of 20997761 is 16779902.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12117361 + 8880400 = 3481^2 + 2980^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20997761 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20997701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10498880 + 10498881.

It is an arithmetic number, because the mean of its divisors is an integer number (10498881).

Almost surely, 2^20997761 is an apocalyptic number.

It is an amenable number.

20997761 is a deficient number, since it is larger than the sum of its proper divisors (1).

20997761 is an equidigital number, since it uses as much as digits as its factorization.

20997761 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 47628, while the sum is 41.

The square root of 20997761 is about 4582.3313935158. The cubic root of 20997761 is about 275.8826121607.

The spelling of 20997761 in words is "twenty million, nine hundred ninety-seven thousand, seven hundred sixty-one".