661958643 has 4 divisors (see below), whose sum is σ = 882611528. Its totient is φ = 441305760.

The previous prime is 661958623. The next prime is 661958657. The reversal of 661958643 is 346859166.

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

It is a de Polignac number, because none of the positive numbers 2^k-661958643 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 661958592 and 661958601.

It is not an unprimeable number, because it can be changed into a prime (661958623) 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, 110326438 + ... + 110326443.

It is an arithmetic number, because the mean of its divisors is an integer number (220652882).

Almost surely, 2^661958643 is an apocalyptic number.

661958643 is a deficient number, since it is larger than the sum of its proper divisors (220652885).

661958643 is a wasteful number, since it uses less digits than its factorization.

661958643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 220652884.

The product of its digits is 933120, while the sum is 48.

The square root of 661958643 is about 25728.5569552589. The cubic root of 661958643 is about 871.5191860687.

The spelling of 661958643 in words is "six hundred sixty-one million, nine hundred fifty-eight thousand, six hundred forty-three".