661401500 has 48 divisors (see below), whose sum is σ = 1447511520. Its totient is φ = 264009600.

The previous prime is 661401493. The next prime is 661401539. The reversal of 661401500 is 5104166.

It is a congruent 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 15 ways as a sum of consecutive naturals, for example, 308432 + ... + 310568.

It is an arithmetic number, because the mean of its divisors is an integer number (30156490).

Almost surely, 2^661401500 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 661401500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (723755760).

661401500 is an abundant number, since it is smaller than the sum of its proper divisors (786110020).

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

661401500 is a wasteful number, since it uses less digits than its factorization.

661401500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2775 (or 2763 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 661401500 is about 25717.7273490486. The cubic root of 661401500 is about 871.2746103145.

Adding to 661401500 its reverse (5104166), we get a palindrome (666505666).

The spelling of 661401500 in words is "six hundred sixty-one million, four hundred one thousand, five hundred".