12640279991 has 4 divisors (see below), whose sum is σ = 12641966400. Its totient is φ = 12638593584.

The previous prime is 12640279973. The next prime is 12640279999. The reversal of 12640279991 is 19997204621.

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

It is a cyclic number.

It is not a de Polignac number, because 12640279991 - 2¹⁴ = 12640263607 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 (12640279999) 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, 831911 + ... + 846968.

It is an arithmetic number, because the mean of its divisors is an integer number (3160491600).

Almost surely, 2^12640279991 is an apocalyptic number.

12640279991 is a deficient number, since it is larger than the sum of its proper divisors (1686409).

12640279991 is an equidigital number, since it uses as much as digits as its factorization.

12640279991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1686408.

The product of its (nonzero) digits is 489888, while the sum is 50.

Adding to 12640279991 its sum of digits (50), we get a square (12640280041 = 112429²).

The spelling of 12640279991 in words is "twelve billion, six hundred forty million, two hundred seventy-nine thousand, nine hundred ninety-one".