642754213781 has 2 divisors, whose sum is σ = 642754213782. Its totient is φ = 642754213780.

The previous prime is 642754213757. The next prime is 642754213823. The reversal of 642754213781 is 187312457246.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 590845882225 + 51908331556 = 768665^2 + 227834^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-642754213781 is a prime.

It is a super-2 number, since 2×642754213781² (a number of 24 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642754210781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321377106890 + 321377106891.

It is an arithmetic number, because the mean of its divisors is an integer number (321377106891).

Almost surely, 2^642754213781 is an apocalyptic number.

It is an amenable number.

642754213781 is a deficient number, since it is larger than the sum of its proper divisors (1).

642754213781 is an equidigital number, since it uses as much as digits as its factorization.

642754213781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2257920, while the sum is 50.

The spelling of 642754213781 in words is "six hundred forty-two billion, seven hundred fifty-four million, two hundred thirteen thousand, seven hundred eighty-one".