644001155 has 16 divisors (see below), whose sum is σ = 884597760. Its totient is φ = 440902752.

The previous prime is 644001133. The next prime is 644001167. The reversal of 644001155 is 551100446.

It is a cyclic number.

It is not a de Polignac number, because 644001155 - 2⁶ = 644001091 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8426 + ... + 36864.

It is an arithmetic number, because the mean of its divisors is an integer number (55287360).

Almost surely, 2^644001155 is an apocalyptic number.

644001155 is a deficient number, since it is larger than the sum of its proper divisors (240596605).

644001155 is a wasteful number, since it uses less digits than its factorization.

644001155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29098.

The product of its (nonzero) digits is 2400, while the sum is 26.

The square root of 644001155 is about 25377.1778375768. The cubic root of 644001155 is about 863.5660271115.

The spelling of 644001155 in words is "six hundred forty-four million, one thousand, one hundred fifty-five".