661288637280 has 288 divisors, whose sum is σ = 2201754096864. Its totient is φ = 166812475392.

The previous prime is 661288637239. The next prime is 661288637293. The reversal of 661288637280 is 82736882166.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (57).

It is a self number, because there is not a number n which added to its sum of digits gives 661288637280.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 133942972 + ... + 133947908.

It is an arithmetic number, because the mean of its divisors is an integer number (7644979503).

Almost surely, 2^661288637280 is an apocalyptic number.

661288637280 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661288637280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1100877048432).

661288637280 is an abundant number, since it is smaller than the sum of its proper divisors (1540465459584).

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

661288637280 is a wasteful number, since it uses less digits than its factorization.

661288637280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5766 (or 5739 counting only the distinct ones).

The product of its (nonzero) digits is 9289728, while the sum is 57.

The spelling of 661288637280 in words is "six hundred sixty-one billion, two hundred eighty-eight million, six hundred thirty-seven thousand, two hundred eighty".