67991 has 8 divisors (see below), whose sum is σ = 84864. Its totient is φ = 52920.

The previous prime is 67987. The next prime is 67993. The reversal of 67991 is 19976.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 67991 - 2² = 67987 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 (67993) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 365 + ... + 518.

It is an arithmetic number, because the mean of its divisors is an integer number (10608).

2⁶⁷⁹⁹¹ is an apocalyptic number.

67991 is a deficient number, since it is larger than the sum of its proper divisors (16873).

67991 is a wasteful number, since it uses less digits than its factorization.

67991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 901.

The product of its digits is 3402, while the sum is 32.

The square root of 67991 is about 260.7508389248. The cubic root of 67991 is about 40.8147502095.

Multiplying 67991 by its sum of digits (32), we get a palindrome (2175712).

It can be divided in two parts, 6 and 7991, that added together give a palindrome (7997).

The spelling of 67991 in words is "sixty-seven thousand, nine hundred ninety-one".