644021262601 has 4 divisors (see below), whose sum is σ = 644157683604. Its totient is φ = 643884841600.

The previous prime is 644021262587. The next prime is 644021262629. The reversal of 644021262601 is 106262120446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 106262120446 = 2 ⋅53131060223.

It can be written as a sum of positive squares in 2 ways, for example, as 458161119376 + 185860143225 = 676876^2 + 431115^2 .

It is a cyclic number.

It is not a de Polignac number, because 644021262601 - 2⁷ = 644021262473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644021260601) 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, 68203420 + ... + 68212861.

It is an arithmetic number, because the mean of its divisors is an integer number (161039420901).

Almost surely, 2^644021262601 is an apocalyptic number.

It is an amenable number.

644021262601 is a deficient number, since it is larger than the sum of its proper divisors (136421003).

644021262601 is a wasteful number, since it uses less digits than its factorization.

644021262601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136421002.

The product of its (nonzero) digits is 27648, while the sum is 34.

The spelling of 644021262601 in words is "six hundred forty-four billion, twenty-one million, two hundred sixty-two thousand, six hundred one".