20912989 has 2 divisors, whose sum is σ = 20912990. Its totient is φ = 20912988.

The previous prime is 20912923. The next prime is 20913037. The reversal of 20912989 is 98921902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20025625 + 887364 = 4475^2 + 942^2 .

It is a cyclic number.

It is not a de Polignac number, because 20912989 - 2⁹ = 20912477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20912189) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10456494 + 10456495.

It is an arithmetic number, because the mean of its divisors is an integer number (10456495).

Almost surely, 2^20912989 is an apocalyptic number.

It is an amenable number.

20912989 is a deficient number, since it is larger than the sum of its proper divisors (1).

20912989 is an equidigital number, since it uses as much as digits as its factorization.

20912989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 40.

The square root of 20912989 is about 4573.0721621247. The cubic root of 20912989 is about 275.5108476926.

The spelling of 20912989 in words is "twenty million, nine hundred twelve thousand, nine hundred eighty-nine".