661131520 has 216 divisors, whose sum is σ = 1879041024. Its totient is φ = 222179328.

The previous prime is 661131517. The next prime is 661131571. The reversal of 661131520 is 25131166.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5205697 + ... + 5205823.

It is an arithmetic number, because the mean of its divisors is an integer number (8699264).

Almost surely, 2^661131520 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661131520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (939520512).

661131520 is an abundant number, since it is smaller than the sum of its proper divisors (1217909504).

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

661131520 is a wasteful number, since it uses less digits than its factorization.

661131520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245 (or 224 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 661131520 is about 25712.4779047061. The cubic root of 661131520 is about 871.1560445454.

Adding to 661131520 its reverse (25131166), we get a palindrome (686262686).

The spelling of 661131520 in words is "six hundred sixty-one million, one hundred thirty-one thousand, five hundred twenty".