1263991999 has 4 divisors (see below), whose sum is σ = 1307577960. Its totient is φ = 1220406040.

The previous prime is 1263991957. The next prime is 1263992029. The reversal of 1263991999 is 9991993621.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9991993621 = 19571 ⋅510551.

It is a cyclic number.

It is not a de Polignac number, because 1263991999 - 2¹³ = 1263983807 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 (1263991199) 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, 21792937 + ... + 21792994.

It is an arithmetic number, because the mean of its divisors is an integer number (326894490).

Almost surely, 2^1263991999 is an apocalyptic number.

1263991999 is a deficient number, since it is larger than the sum of its proper divisors (43585961).

1263991999 is an equidigital number, since it uses as much as digits as its factorization.

1263991999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43585960.

The product of its digits is 2125764, while the sum is 58.

The square root of 1263991999 is about 35552.6651462306. The cubic root of 1263991999 is about 1081.2217537967.

The spelling of 1263991999 in words is "one billion, two hundred sixty-three million, nine hundred ninety-one thousand, nine hundred ninety-nine".