661644621340 has 24 divisors (see below), whose sum is σ = 1415669814720. Its totient is φ = 259664303808.

The previous prime is 661644621293. The next prime is 661644621367. The reversal of 661644621340 is 43126446166.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 312095460 + ... + 312097579.

It is an arithmetic number, because the mean of its divisors is an integer number (58986242280).

Almost surely, 2^661644621340 is an apocalyptic number.

It is an amenable number.

661644621340 is an abundant number, since it is smaller than the sum of its proper divisors (754025193380).

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

661644621340 is a wasteful number, since it uses less digits than its factorization.

661644621340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 624193101 (or 624193099 counting only the distinct ones).

The product of its (nonzero) digits is 497664, while the sum is 43.

The spelling of 661644621340 in words is "six hundred sixty-one billion, six hundred forty-four million, six hundred twenty-one thousand, three hundred forty".