20787491 has 2 divisors, whose sum is σ = 20787492. Its totient is φ = 20787490.

The previous prime is 20787479. The next prime is 20787493. The reversal of 20787491 is 19478702.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20787491 - 2¹⁸ = 20525347 is a prime.

Together with 20787493, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20787493) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10393745 + 10393746.

It is an arithmetic number, because the mean of its divisors is an integer number (10393746).

Almost surely, 2^20787491 is an apocalyptic number.

20787491 is a deficient number, since it is larger than the sum of its proper divisors (1).

20787491 is an equidigital number, since it uses as much as digits as its factorization.

20787491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28224, while the sum is 38.

The square root of 20787491 is about 4559.3301043026. The cubic root of 20787491 is about 274.9586317938.

The spelling of 20787491 in words is "twenty million, seven hundred eighty-seven thousand, four hundred ninety-one".