661520431650 has 192 divisors, whose sum is σ = 1790860377600. Its totient is φ = 160619397120.

The previous prime is 661520431609. The next prime is 661520431657. The reversal of 661520431650 is 56134025166.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a junction number, because it is equal to n+sod(n) for n = 661520431599 and 661520431608.

It is not an unprimeable number, because it can be changed into a prime (661520431657) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 310717786 + ... + 310719914.

It is an arithmetic number, because the mean of its divisors is an integer number (9327397800).

Almost surely, 2^661520431650 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661520431650, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (895430188800).

661520431650 is an abundant number, since it is smaller than the sum of its proper divisors (1129339945950).

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

661520431650 is a wasteful number, since it uses less digits than its factorization.

661520431650 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4253 (or 4248 counting only the distinct ones).

The product of its (nonzero) digits is 129600, while the sum is 39.

The spelling of 661520431650 in words is "six hundred sixty-one billion, five hundred twenty million, four hundred thirty-one thousand, six hundred fifty".