640546861 has 2 divisors, whose sum is σ = 640546862. Its totient is φ = 640546860.

The previous prime is 640546853. The next prime is 640546871. The reversal of 640546861 is 168645046.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 532178761 + 108368100 = 23069^2 + 10410^2 .

It is a cyclic number.

It is not a de Polignac number, because 640546861 - 2³ = 640546853 is a prime.

It is a super-2 number, since 2×640546861² = 820600562273906642, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640546871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320273430 + 320273431.

It is an arithmetic number, because the mean of its divisors is an integer number (320273431).

Almost surely, 2^640546861 is an apocalyptic number.

It is an amenable number.

640546861 is a deficient number, since it is larger than the sum of its proper divisors (1).

640546861 is an equidigital number, since it uses as much as digits as its factorization.

640546861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 138240, while the sum is 40.

The square root of 640546861 is about 25309.0272630143. The cubic root of 640546861 is about 862.0192595328.

The spelling of 640546861 in words is "six hundred forty million, five hundred forty-six thousand, eight hundred sixty-one".