661497678 has 40 divisors (see below), whose sum is σ = 1490875848. Its totient is φ = 219215376.

The previous prime is 661497671. The next prime is 661497679. The reversal of 661497678 is 876794166.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661497671) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 16225 + ... + 39827.

Almost surely, 2^661497678 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661497678, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (745437924).

661497678 is an abundant number, since it is smaller than the sum of its proper divisors (829378170).

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

661497678 is a wasteful number, since it uses less digits than its factorization.

661497678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23790 (or 23781 counting only the distinct ones).

The product of its digits is 3048192, while the sum is 54.

The square root of 661497678 is about 25719.5971585871. The cubic root of 661497678 is about 871.3168405322.

The spelling of 661497678 in words is "six hundred sixty-one million, four hundred ninety-seven thousand, six hundred seventy-eight".