67161781 has 4 divisors (see below), whose sum is σ = 71112492. Its totient is φ = 63211072.

The previous prime is 67161761. The next prime is 67161799. The reversal of 67161781 is 18716176.

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 26316900 + 40844881 = 5130^2 + 6391^2 .

It is a cyclic number.

It is not a de Polignac number, because 67161781 - 2²⁵ = 33607349 is a prime.

It is a super-2 number, since 2×67161781² = 9021409654183922, which contains 22 as substring.

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 67161781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (67161701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1975330 + ... + 1975363.

It is an arithmetic number, because the mean of its divisors is an integer number (17778123).

Almost surely, 2^67161781 is an apocalyptic number.

It is an amenable number.

67161781 is a deficient number, since it is larger than the sum of its proper divisors (3950711).

67161781 is a wasteful number, since it uses less digits than its factorization.

67161781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3950710.

The product of its digits is 14112, while the sum is 37.

The square root of 67161781 is about 8195.2291609204. The cubic root of 67161781 is about 406.4814534026.

The spelling of 67161781 in words is "sixty-seven million, one hundred sixty-one thousand, seven hundred eighty-one".