643661370 has 128 divisors (see below), whose sum is σ = 1933148160. Its totient is φ = 150984000.

The previous prime is 643661357. The next prime is 643661377. The reversal of 643661370 is 73166346.

It is a happy number.

643661370 is a `hidden beast` number, since 6 + 4 + 36 + 613 + 7 + 0 = 666.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (643661377) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 88575 + ... + 95565.

It is an arithmetic number, because the mean of its divisors is an integer number (15102720).

Almost surely, 2^643661370 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 643661370, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (966574080).

643661370 is an abundant number, since it is smaller than the sum of its proper divisors (1289486790).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

643661370 is a wasteful number, since it uses less digits than its factorization.

643661370 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7049 (or 7043 counting only the distinct ones).

The product of its (nonzero) digits is 54432, while the sum is 36.

The square root of 643661370 is about 25370.4822579312. The cubic root of 643661370 is about 863.4141234486.

The spelling of 643661370 in words is "six hundred forty-three million, six hundred sixty-one thousand, three hundred seventy".