661505620 has 12 divisors (see below), whose sum is σ = 1389161844. Its totient is φ = 264602240.

The previous prime is 661505609. The next prime is 661505627. The reversal of 661505620 is 26505166.

It can be written as a sum of positive squares in 2 ways, for example, as 413064976 + 248440644 = 20324^2 + 15762^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661505627) 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, 16537621 + ... + 16537660.

It is an arithmetic number, because the mean of its divisors is an integer number (115763487).

Almost surely, 2^661505620 is an apocalyptic number.

It is an amenable number.

661505620 is an abundant number, since it is smaller than the sum of its proper divisors (727656224).

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

661505620 is a wasteful number, since it uses less digits than its factorization.

661505620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33075290 (or 33075288 counting only the distinct ones).

The product of its (nonzero) digits is 10800, while the sum is 31.

The square root of 661505620 is about 25719.7515540100. The cubic root of 661505620 is about 871.3203275541.

The spelling of 661505620 in words is "six hundred sixty-one million, five hundred five thousand, six hundred twenty".