68157781 has 4 divisors (see below), whose sum is σ = 68443200. Its totient is φ = 67872364.

The previous prime is 68157773. The next prime is 68157787. The reversal of 68157781 is 18775186.

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 68157781 - 2³ = 68157773 is a prime.

It is a super-2 number, since 2×68157781² = 9290966221687922, which 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 (68157787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 142351 + ... + 142828.

It is an arithmetic number, because the mean of its divisors is an integer number (17110800).

Almost surely, 2^68157781 is an apocalyptic number.

It is an amenable number.

68157781 is a deficient number, since it is larger than the sum of its proper divisors (285419).

68157781 is a wasteful number, since it uses less digits than its factorization.

68157781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 285418.

The product of its digits is 94080, while the sum is 43.

The square root of 68157781 is about 8255.7725864997. The cubic root of 68157781 is about 408.4809563515.

The spelling of 68157781 in words is "sixty-eight million, one hundred fifty-seven thousand, seven hundred eighty-one".