1271991 has 24 divisors (see below), whose sum is σ = 2093040. Its totient is φ = 682752.

The previous prime is 1271987. The next prime is 1271999. The reversal of 1271991 is 1991721.

It is not a de Polignac number, because 1271991 - 2² = 1271987 is a prime.

It is a super-2 number, since 2×1271991² = 3235922208162, which contains 22 as substring.

1271991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1271999) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2245 + ... + 2753.

It is an arithmetic number, because the mean of its divisors is an integer number (87210).

2^1271991 is an apocalyptic number.

1271991 is a deficient number, since it is larger than the sum of its proper divisors (821049).

1271991 is a wasteful number, since it uses less digits than its factorization.

1271991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 543 (or 536 counting only the distinct ones).

The product of its digits is 1134, while the sum is 30.

The square root of 1271991 is about 1127.8257844189. The cubic root of 1271991 is about 108.3497747564.

The spelling of 1271991 in words is "one million, two hundred seventy-one thousand, nine hundred ninety-one".