643730678978 has 4 divisors (see below), whose sum is σ = 965596018470. Its totient is φ = 321865339488.

The previous prime is 643730678977. The next prime is 643730679043. The reversal of 643730678978 is 879876037346.

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

It can be written as a sum of positive squares in only one way, i.e., 435094586689 + 208636092289 = 659617^2 + 456767^2 .

It is a super-2 number, since 2×643730678978² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (643730678977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160932669743 + ... + 160932669746.

Almost surely, 2^643730678978 is an apocalyptic number.

643730678978 is a deficient number, since it is larger than the sum of its proper divisors (321865339492).

643730678978 is a wasteful number, since it uses less digits than its factorization.

643730678978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321865339491.

The product of its (nonzero) digits is 256048128, while the sum is 68.

The spelling of 643730678978 in words is "six hundred forty-three billion, seven hundred thirty million, six hundred seventy-eight thousand, nine hundred seventy-eight".