67691721 has 4 divisors (see below), whose sum is σ = 90255632. Its totient is φ = 45127812.

The previous prime is 67691717. The next prime is 67691747. The reversal of 67691721 is 12719676.

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 not a de Polignac number, because 67691721 - 2² = 67691717 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 67691721.

It is not an unprimeable number, because it can be changed into a prime (67691791) 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, 11281951 + ... + 11281956.

It is an arithmetic number, because the mean of its divisors is an integer number (22563908).

Almost surely, 2^67691721 is an apocalyptic number.

It is an amenable number.

67691721 is a deficient number, since it is larger than the sum of its proper divisors (22563911).

67691721 is a wasteful number, since it uses less digits than its factorization.

67691721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22563910.

The product of its digits is 31752, while the sum is 39.

The square root of 67691721 is about 8227.4978577937. The cubic root of 67691721 is about 407.5477676198.

The spelling of 67691721 in words is "sixty-seven million, six hundred ninety-one thousand, seven hundred twenty-one".