661640406 has 16 divisors (see below), whose sum is σ = 1512321024. Its totient is φ = 189040104.

The previous prime is 661640389. The next prime is 661640407. The reversal of 661640406 is 604046166.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661640407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7876630 + ... + 7876713.

It is an arithmetic number, because the mean of its divisors is an integer number (94520064).

Almost surely, 2^661640406 is an apocalyptic number.

661640406 is an abundant number, since it is smaller than the sum of its proper divisors (850680618).

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

661640406 is a wasteful number, since it uses less digits than its factorization.

661640406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15753355.

The product of its (nonzero) digits is 20736, while the sum is 33.

The square root of 661640406 is about 25722.3717024694. The cubic root of 661640406 is about 871.3795025646.

The spelling of 661640406 in words is "six hundred sixty-one million, six hundred forty thousand, four hundred six".