643690543906 has 16 divisors (see below), whose sum is σ = 992778751800. Its totient is φ = 312875716608.

The previous prime is 643690543871. The next prime is 643690543943. The reversal of 643690543906 is 609345096346.

It can be written as a sum of positive squares in 4 ways, for example, as 617574367881 + 26116176025 = 785859^2 + 161605^2 .

It is a super-2 number, since 2×643690543906² (a number of 24 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27844191 + ... + 27867298.

Almost surely, 2^643690543906 is an apocalyptic number.

643690543906 is a deficient number, since it is larger than the sum of its proper divisors (349088207894).

643690543906 is a wasteful number, since it uses less digits than its factorization.

643690543906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55711653.

The product of its (nonzero) digits is 12597120, while the sum is 55.

The spelling of 643690543906 in words is "six hundred forty-three billion, six hundred ninety million, five hundred forty-three thousand, nine hundred six".