661243919 has 12 divisors (see below), whose sum is σ = 780879312. Its totient is φ = 548491680.

The previous prime is 661243907. The next prime is 661243937. The reversal of 661243919 is 919342166.

661243919 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 661243919 - 2⁸ = 661243663 is a prime.

It is a super-2 number, since 2×661243919² = 874487040828957122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661243019) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 42422 + ... + 55875.

It is an arithmetic number, because the mean of its divisors is an integer number (65073276).

Almost surely, 2^661243919 is an apocalyptic number.

661243919 is a deficient number, since it is larger than the sum of its proper divisors (119635393).

661243919 is an equidigital number, since it uses as much as digits as its factorization.

661243919 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 98366 (or 98335 counting only the distinct ones).

The product of its digits is 69984, while the sum is 41.

The square root of 661243919 is about 25714.6635015899. The cubic root of 661243919 is about 871.2054101743.

The spelling of 661243919 in words is "six hundred sixty-one million, two hundred forty-three thousand, nine hundred nineteen".