640973777 has 2 divisors, whose sum is σ = 640973778. Its totient is φ = 640973776.

The previous prime is 640973741. The next prime is 640973813. The reversal of 640973777 is 777379046.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (640973741) and next prime (640973813).

It can be written as a sum of positive squares in only one way, i.e., 350475841 + 290497936 = 18721^2 + 17044^2 .

It is a cyclic number.

It is not a de Polignac number, because 640973777 - 2¹⁴ = 640957393 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (640973717) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320486888 + 320486889.

It is an arithmetic number, because the mean of its divisors is an integer number (320486889).

Almost surely, 2^640973777 is an apocalyptic number.

It is an amenable number.

640973777 is a deficient number, since it is larger than the sum of its proper divisors (1).

640973777 is an equidigital number, since it uses as much as digits as its factorization.

640973777 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1555848, while the sum is 50.

The square root of 640973777 is about 25317.4599239339. The cubic root of 640973777 is about 862.2107251428.

The spelling of 640973777 in words is "six hundred forty million, nine hundred seventy-three thousand, seven hundred seventy-seven".