643879531 has 4 divisors (see below), whose sum is σ = 647601552. Its totient is φ = 640157512.

The previous prime is 643879487. The next prime is 643879571. The reversal of 643879531 is 135978346.

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

It is a cyclic number.

It is not a de Polignac number, because 643879531 - 2¹¹ = 643877483 is a prime.

It is a super-2 number, since 2×643879531² = 829161700881559922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643879571) 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, 1860751 + ... + 1861096.

It is an arithmetic number, because the mean of its divisors is an integer number (161900388).

Almost surely, 2^643879531 is an apocalyptic number.

643879531 is a deficient number, since it is larger than the sum of its proper divisors (3722021).

643879531 is a wasteful number, since it uses less digits than its factorization.

643879531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3722020.

The product of its digits is 544320, while the sum is 46.

The square root of 643879531 is about 25374.7813980732. The cubic root of 643879531 is about 863.5116602489.

The spelling of 643879531 in words is "six hundred forty-three million, eight hundred seventy-nine thousand, five hundred thirty-one".