642709605781 has 4 divisors (see below), whose sum is σ = 642744359712. Its totient is φ = 642674851852.

The previous prime is 642709605757. The next prime is 642709605787. The reversal of 642709605781 is 187506907246.

642709605781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 642709605781 - 2¹⁵ = 642709573013 is a prime.

It is a super-2 number, since 2×642709605781² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642709605787) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17349211 + ... + 17386216.

It is an arithmetic number, because the mean of its divisors is an integer number (160686089928).

Almost surely, 2^642709605781 is an apocalyptic number.

It is an amenable number.

642709605781 is a deficient number, since it is larger than the sum of its proper divisors (34753931).

642709605781 is a wasteful number, since it uses less digits than its factorization.

642709605781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34753930.

The product of its (nonzero) digits is 5080320, while the sum is 55.

The spelling of 642709605781 in words is "six hundred forty-two billion, seven hundred nine million, six hundred five thousand, seven hundred eighty-one".