643639744757 has 2 divisors, whose sum is σ = 643639744758. Its totient is φ = 643639744756.

The previous prime is 643639744733. The next prime is 643639744763. The reversal of 643639744757 is 757447936346.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 510787513636 + 132852231121 = 714694^2 + 364489^2 .

It is a cyclic number.

It is not a de Polignac number, because 643639744757 - 2¹² = 643639740661 is a prime.

It is a super-2 number, since 2×643639744757² (a number of 24 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 643639744693 and 643639744702.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643639744717) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321819872378 + 321819872379.

It is an arithmetic number, because the mean of its divisors is an integer number (321819872379).

Almost surely, 2^643639744757 is an apocalyptic number.

It is an amenable number.

643639744757 is a deficient number, since it is larger than the sum of its proper divisors (1).

643639744757 is an equidigital number, since it uses as much as digits as its factorization.

643639744757 is an evil number, because the sum of its binary digits is even.

The product of its digits is 320060160, while the sum is 65.

The spelling of 643639744757 in words is "six hundred forty-three billion, six hundred thirty-nine million, seven hundred forty-four thousand, seven hundred fifty-seven".