155781681 has 16 divisors (see below), whose sum is σ = 230869440. Its totient is φ = 92630720.

The previous prime is 155781671. The next prime is 155781697. The reversal of 155781681 is 186187551.

It is a cyclic number.

It is not a de Polignac number, because 155781681 - 2²⁵ = 122227249 is a prime.

It is a super-2 number, since 2×155781681² = 48535864270371522, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (155781611) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 42786 + ... + 46283.

It is an arithmetic number, because the mean of its divisors is an integer number (14429340).

Almost surely, 2^155781681 is an apocalyptic number.

155781681 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

155781681 is a deficient number, since it is larger than the sum of its proper divisors (75087759).

155781681 is a wasteful number, since it uses less digits than its factorization.

155781681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89136.

The product of its digits is 67200, while the sum is 42.

The square root of 155781681 is about 12481.2531822730. The cubic root of 155781681 is about 538.0700205525.

It can be divided in two parts, 1557 and 81681, that added together give a palindrome (83238).

The spelling of 155781681 in words is "one hundred fifty-five million, seven hundred eighty-one thousand, six hundred eighty-one".