6691138873781 has 4 divisors (see below), whose sum is σ = 6731205573792. Its totient is φ = 6651072173772.

The previous prime is 6691138873709. The next prime is 6691138873789. The reversal of 6691138873781 is 1873788311966.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 6691138873781 - 2²⁶ = 6691071764917 is a prime.

It is a super-2 number, since 2×6691138873781² (a number of 26 digits) contains 22 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 (6691138873789) 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, 20033349755 + ... + 20033350088.

It is an arithmetic number, because the mean of its divisors is an integer number (1682801393448).

Almost surely, 2^{6691138873781} is an apocalyptic number.

It is an amenable number.

6691138873781 is a deficient number, since it is larger than the sum of its proper divisors (40066700011).

6691138873781 is a wasteful number, since it uses less digits than its factorization.

6691138873781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40066700010.

The product of its digits is 73156608, while the sum is 68.

The spelling of 6691138873781 in words is "six trillion, six hundred ninety-one billion, one hundred thirty-eight million, eight hundred seventy-three thousand, seven hundred eighty-one".