640661149 has 2 divisors, whose sum is σ = 640661150. Its totient is φ = 640661148.

The previous prime is 640661137. The next prime is 640661237. The reversal of 640661149 is 941166046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 634133124 + 6528025 = 25182^2 + 2555^2 .

It is a cyclic number.

It is not a de Polignac number, because 640661149 - 2¹⁵ = 640628381 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640661129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320330574 + 320330575.

It is an arithmetic number, because the mean of its divisors is an integer number (320330575).

Almost surely, 2^640661149 is an apocalyptic number.

It is an amenable number.

640661149 is a deficient number, since it is larger than the sum of its proper divisors (1).

640661149 is an equidigital number, since it uses as much as digits as its factorization.

640661149 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 37.

The square root of 640661149 is about 25311.2850128159. The cubic root of 640661149 is about 862.0705243735.

The spelling of 640661149 in words is "six hundred forty million, six hundred sixty-one thousand, one hundred forty-nine".