640897771 has 2 divisors, whose sum is σ = 640897772. Its totient is φ = 640897770.

The previous prime is 640897657. The next prime is 640897787. The reversal of 640897771 is 177798046.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640897771 - 2⁷ = 640897643 is a prime.

It is not a weakly prime, because it can be changed into another prime (640807771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320448885 + 320448886.

It is an arithmetic number, because the mean of its divisors is an integer number (320448886).

Almost surely, 2^640897771 is an apocalyptic number.

640897771 is a deficient number, since it is larger than the sum of its proper divisors (1).

640897771 is an equidigital number, since it uses as much as digits as its factorization.

640897771 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 592704, while the sum is 49.

The square root of 640897771 is about 25315.9588204753. The cubic root of 640897771 is about 862.1766437804.

The spelling of 640897771 in words is "six hundred forty million, eight hundred ninety-seven thousand, seven hundred seventy-one".