641987491 has 2 divisors, whose sum is σ = 641987492. Its totient is φ = 641987490.

The previous prime is 641987483. The next prime is 641987503. The reversal of 641987491 is 194789146.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 641987491 - 2³ = 641987483 is a prime.

It is not a weakly prime, because it can be changed into another prime (641987441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320993745 + 320993746.

It is an arithmetic number, because the mean of its divisors is an integer number (320993746).

Almost surely, 2^641987491 is an apocalyptic number.

641987491 is a deficient number, since it is larger than the sum of its proper divisors (1).

641987491 is an equidigital number, since it uses as much as digits as its factorization.

641987491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 435456, while the sum is 49.

The square root of 641987491 is about 25337.4720720122. The cubic root of 641987491 is about 862.6650207528.

The spelling of 641987491 in words is "six hundred forty-one million, nine hundred eighty-seven thousand, four hundred ninety-one".