661511839 has 4 divisors (see below), whose sum is σ = 661563280. Its totient is φ = 661460400.

The previous prime is 661511833. The next prime is 661511849. The reversal of 661511839 is 938115166.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 938115166 = 2 ⋅469057583.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661511839 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661511833) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12739 + ... + 38539.

It is an arithmetic number, because the mean of its divisors is an integer number (165390820).

Almost surely, 2^661511839 is an apocalyptic number.

661511839 is a deficient number, since it is larger than the sum of its proper divisors (51441).

661511839 is a wasteful number, since it uses less digits than its factorization.

661511839 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51440.

The product of its digits is 38880, while the sum is 40.

The square root of 661511839 is about 25719.8724530274. The cubic root of 661511839 is about 871.3230580545.

The spelling of 661511839 in words is "six hundred sixty-one million, five hundred eleven thousand, eight hundred thirty-nine".