661426646472820 has 48 divisors (see below), whose sum is σ = 1397878949819520. Its totient is φ = 262878746592384.

The previous prime is 661426646472799. The next prime is 661426646472833. The reversal of 661426646472820 is 28274646624166.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 120526327 + ... + 125894593.

It is an arithmetic number, because the mean of its divisors is an integer number (29122478121240).

Almost surely, 2^{661426646472820} is an apocalyptic number.

It is an amenable number.

661426646472820 is an abundant number, since it is smaller than the sum of its proper divisors (736452303346700).

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

661426646472820 is a wasteful number, since it uses less digits than its factorization.

661426646472820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5407672 (or 5407670 counting only the distinct ones).

The product of its (nonzero) digits is 222953472, while the sum is 64.

The spelling of 661426646472820 in words is "six hundred sixty-one trillion, four hundred twenty-six billion, six hundred forty-six million, four hundred seventy-two thousand, eight hundred twenty".