644214531 has 4 divisors (see below), whose sum is σ = 858952712. Its totient is φ = 429476352.

The previous prime is 644214491. The next prime is 644214547. The reversal of 644214531 is 135412446.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 644214531 - 2¹⁵ = 644181763 is a prime.

It is a super-2 number, since 2×644214531² = 830024723903099922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644210531) 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, 107369086 + ... + 107369091.

It is an arithmetic number, because the mean of its divisors is an integer number (214738178).

Almost surely, 2^644214531 is an apocalyptic number.

644214531 is a deficient number, since it is larger than the sum of its proper divisors (214738181).

644214531 is a wasteful number, since it uses less digits than its factorization.

644214531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214738180.

The product of its digits is 11520, while the sum is 30.

The square root of 644214531 is about 25381.3815817816. The cubic root of 644214531 is about 863.6613912871.

Adding to 644214531 its reverse (135412446), we get a palindrome (779626977).

The spelling of 644214531 in words is "six hundred forty-four million, two hundred fourteen thousand, five hundred thirty-one".