661321098 has 56 divisors (see below), whose sum is σ = 1492272900. Its totient is φ = 219703104.

The previous prime is 661321081. The next prime is 661321117. The reversal of 661321098 is 890123166.

It can be written as a sum of positive squares in 2 ways, for example, as 656538129 + 4782969 = 25623^2 + 2187^2 .

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 595768 + ... + 596876.

Almost surely, 2^661321098 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661321098, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (746136450).

661321098 is an abundant number, since it is smaller than the sum of its proper divisors (830951802).

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

661321098 is a wasteful number, since it uses less digits than its factorization.

661321098 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1538 (or 1523 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 661321098 is about 25716.1641385336. The cubic root of 661321098 is about 871.2393039436.

The spelling of 661321098 in words is "six hundred sixty-one million, three hundred twenty-one thousand, ninety-eight".