1231991431 has 4 divisors (see below), whose sum is σ = 1343990664. Its totient is φ = 1119992200.

The previous prime is 1231991419. The next prime is 1231991443. The reversal of 1231991431 is 1341991321.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (1231991419) and next prime (1231991443).

It is a cyclic number.

It is not a de Polignac number, because 1231991431 - 2⁵ = 1231991399 is a prime.

It is a super-2 number, since 2×1231991431² = 3035605772114855522, 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 (1231991531) 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, 55999600 + ... + 55999621.

It is an arithmetic number, because the mean of its divisors is an integer number (335997666).

Almost surely, 2^1231991431 is an apocalyptic number.

1231991431 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1231991431 is a deficient number, since it is larger than the sum of its proper divisors (111999233).

1231991431 is a wasteful number, since it uses less digits than its factorization.

1231991431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111999232.

The product of its digits is 5832, while the sum is 34.

The square root of 1231991431 is about 35099.7354833338. The cubic root of 1231991431 is about 1072.0191967561.

The spelling of 1231991431 in words is "one billion, two hundred thirty-one million, nine hundred ninety-one thousand, four hundred thirty-one".