11947991 has 16 divisors (see below), whose sum is σ = 13916448. Its totient is φ = 10137600.

The previous prime is 11947981. The next prime is 11947993. The reversal of 11947991 is 19974911.

It is a de Polignac number, because none of the positive numbers 2^k-11947991 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 (11947993) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33671 + ... + 34023.

It is an arithmetic number, because the mean of its divisors is an integer number (869778).

Almost surely, 2^11947991 is an apocalyptic number.

11947991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

11947991 is a deficient number, since it is larger than the sum of its proper divisors (1968457).

11947991 is a wasteful number, since it uses less digits than its factorization.

11947991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 562.

The product of its digits is 20412, while the sum is 41.

The square root of 11947991 is about 3456.5866110948. The cubic root of 11947991 is about 228.6116170592.

The spelling of 11947991 in words is "eleven million, nine hundred forty-seven thousand, nine hundred ninety-one".