641720887 has 2 divisors, whose sum is σ = 641720888. Its totient is φ = 641720886.

The previous prime is 641720869. The next prime is 641720897. The reversal of 641720887 is 788027146.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-641720887 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (641720867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320860443 + 320860444.

It is an arithmetic number, because the mean of its divisors is an integer number (320860444).

Almost surely, 2^641720887 is an apocalyptic number.

641720887 is a deficient number, since it is larger than the sum of its proper divisors (1).

641720887 is an equidigital number, since it uses as much as digits as its factorization.

641720887 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 150528, while the sum is 43.

The square root of 641720887 is about 25332.2104641502. The cubic root of 641720887 is about 862.5455886286.

The spelling of 641720887 in words is "six hundred forty-one million, seven hundred twenty thousand, eight hundred eighty-seven".