644026087 has 4 divisors (see below), whose sum is σ = 644112040. Its totient is φ = 643940136.

The previous prime is 644026063. The next prime is 644026099. The reversal of 644026087 is 780620446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 780620446 = 2 ⋅390310223.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644026087 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644026027) 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, 30537 + ... + 47122.

It is an arithmetic number, because the mean of its divisors is an integer number (161028010).

Almost surely, 2^644026087 is an apocalyptic number.

644026087 is a deficient number, since it is larger than the sum of its proper divisors (85953).

644026087 is an equidigital number, since it uses as much as digits as its factorization.

644026087 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85952.

The product of its (nonzero) digits is 64512, while the sum is 37.

The square root of 644026087 is about 25377.6690615982. The cubic root of 644026087 is about 863.5771710617.

The spelling of 644026087 in words is "six hundred forty-four million, twenty-six thousand, eighty-seven".