643537631 has 16 divisors (see below), whose sum is σ = 738194688. Its totient is φ = 555297600.

The previous prime is 643537621. The next prime is 643537639. The reversal of 643537631 is 136735346.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-643537631 is a prime.

It is a super-2 number, since 2×643537631² = 828281365026184322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643537639) 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 15 ways as a sum of consecutive naturals, for example, 23435 + ... + 42851.

It is an arithmetic number, because the mean of its divisors is an integer number (46137168).

Almost surely, 2^643537631 is an apocalyptic number.

643537631 is a deficient number, since it is larger than the sum of its proper divisors (94657057).

643537631 is a wasteful number, since it uses less digits than its factorization.

643537631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19582.

The product of its digits is 136080, while the sum is 38.

The square root of 643537631 is about 25368.0434996473. The cubic root of 643537631 is about 863.3587916379.

The spelling of 643537631 in words is "six hundred forty-three million, five hundred thirty-seven thousand, six hundred thirty-one".