661511550 has 96 divisors (see below), whose sum is σ = 1910449152. Its totient is φ = 148337280.

The previous prime is 661511509. The next prime is 661511551. The reversal of 661511550 is 55115166.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661511551) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 49707 + ... + 61593.

It is an arithmetic number, because the mean of its divisors is an integer number (19900512).

Almost surely, 2^661511550 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661511550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (955224576).

661511550 is an abundant number, since it is smaller than the sum of its proper divisors (1248937602).

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

661511550 is a wasteful number, since it uses less digits than its factorization.

661511550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11962 (or 11957 counting only the distinct ones).

The product of its (nonzero) digits is 4500, while the sum is 30.

The square root of 661511550 is about 25719.8668348030. The cubic root of 661511550 is about 871.3229311672.

The spelling of 661511550 in words is "six hundred sixty-one million, five hundred eleven thousand, five hundred fifty".