1263991 has 4 divisors (see below), whose sum is σ = 1275912. Its totient is φ = 1252072.

The previous prime is 1263979. The next prime is 1264009. The reversal of 1263991 is 1993621.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1993621 = 7 ⋅284803.

It is a cyclic number.

It is not a de Polignac number, because 1263991 - 2⁷ = 1263863 is a prime.

It is a super-3 number, since 3×1263991³ = 6058333819545453813, which contains 333 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 (1263931) 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, 5800 + ... + 6013.

It is an arithmetic number, because the mean of its divisors is an integer number (318978).

2^1263991 is an apocalyptic number.

1263991 is a deficient number, since it is larger than the sum of its proper divisors (11921).

1263991 is a wasteful number, since it uses less digits than its factorization.

1263991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11920.

The product of its digits is 2916, while the sum is 31.

The square root of 1263991 is about 1124.2735432269. The cubic root of 1263991 is about 108.1221468948.

The spelling of 1263991 in words is "one million, two hundred sixty-three thousand, nine hundred ninety-one".