67906721 has 4 divisors (see below), whose sum is σ = 71901252. Its totient is φ = 63912192.

The previous prime is 67906691. The next prime is 67906747. The reversal of 67906721 is 12760976.

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

It can be written as a sum of positive squares in 2 ways, for example, as 53949025 + 13957696 = 7345^2 + 3736^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-67906721 is a prime.

It is a super-2 number, since 2×67906721² = 9222645513943682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (67906781) 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, 1997240 + ... + 1997273.

It is an arithmetic number, because the mean of its divisors is an integer number (17975313).

Almost surely, 2^67906721 is an apocalyptic number.

It is an amenable number.

67906721 is a deficient number, since it is larger than the sum of its proper divisors (3994531).

67906721 is a wasteful number, since it uses less digits than its factorization.

67906721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3994530.

The product of its (nonzero) digits is 31752, while the sum is 38.

The square root of 67906721 is about 8240.5534401519. The cubic root of 67906721 is about 407.9787911089.

The spelling of 67906721 in words is "sixty-seven million, nine hundred six thousand, seven hundred twenty-one".