20291989 has 2 divisors, whose sum is σ = 20291990. Its totient is φ = 20291988.

The previous prime is 20291987. The next prime is 20292037. The reversal of 20291989 is 98919202.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12215025 + 8076964 = 3495^2 + 2842^2 .

It is a cyclic number.

It is not a de Polignac number, because 20291989 - 2¹ = 20291987 is a prime.

It is a super-2 number, since 2×20291989² = 823529635152242, which contains 22 as substring.

Together with 20291987, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20291983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10145994 + 10145995.

It is an arithmetic number, because the mean of its divisors is an integer number (10145995).

Almost surely, 2^20291989 is an apocalyptic number.

It is an amenable number.

20291989 is a deficient number, since it is larger than the sum of its proper divisors (1).

20291989 is an equidigital number, since it uses as much as digits as its factorization.

20291989 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 20291989 is about 4504.6630284628. The cubic root of 20291989 is about 272.7563516435.

The spelling of 20291989 in words is "twenty million, two hundred ninety-one thousand, nine hundred eighty-nine".