644970427 has 4 divisors (see below), whose sum is σ = 650998296. Its totient is φ = 638942560.

The previous prime is 644970413. The next prime is 644970433. The reversal of 644970427 is 724079446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 724079446 = 2 ⋅362039723.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644970427 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644970437) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3013774 + ... + 3013987.

It is an arithmetic number, because the mean of its divisors is an integer number (162749574).

Almost surely, 2^644970427 is an apocalyptic number.

644970427 is a deficient number, since it is larger than the sum of its proper divisors (6027869).

644970427 is a wasteful number, since it uses less digits than its factorization.

644970427 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6027868.

The product of its (nonzero) digits is 338688, while the sum is 43.

The square root of 644970427 is about 25396.2679738579. The cubic root of 644970427 is about 863.9990546936. Note that the first 3 decimals are identical.

The spelling of 644970427 in words is "six hundred forty-four million, nine hundred seventy thousand, four hundred twenty-seven".