1231557861 has 8 divisors (see below), whose sum is σ = 1653098400. Its totient is φ = 815527952.

The previous prime is 1231557851. The next prime is 1231557893. The reversal of 1231557861 is 1687551321.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1231557861 - 2¹⁵ = 1231525093 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1231557851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1377135 + ... + 1378028.

It is an arithmetic number, because the mean of its divisors is an integer number (206637300).

Almost surely, 2^1231557861 is an apocalyptic number.

It is an amenable number.

1231557861 is a deficient number, since it is larger than the sum of its proper divisors (421540539).

1231557861 is a wasteful number, since it uses less digits than its factorization.

1231557861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2755315.

The product of its digits is 50400, while the sum is 39.

The square root of 1231557861 is about 35093.5586824705. The cubic root of 1231557861 is about 1071.8934248049.

The spelling of 1231557861 in words is "one billion, two hundred thirty-one million, five hundred fifty-seven thousand, eight hundred sixty-one".