155666681 has 4 divisors (see below), whose sum is σ = 157178112. Its totient is φ = 154155252.

The previous prime is 155666669. The next prime is 155666683. The reversal of 155666681 is 186666551.

155666681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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, and also an emirpimes, since its reverse is a distinct semiprime: 186666551 = 23 ⋅8115937.

It is a cyclic number.

It is not a de Polignac number, because 155666681 - 2²⁶ = 88557817 is a prime.

It is a super-2 number, since 2×155666681² = 48464231147111522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (155666683) 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, 755561 + ... + 755766.

It is an arithmetic number, because the mean of its divisors is an integer number (39294528).

Almost surely, 2^155666681 is an apocalyptic number.

It is an amenable number.

155666681 is a deficient number, since it is larger than the sum of its proper divisors (1511431).

155666681 is a wasteful number, since it uses less digits than its factorization.

155666681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1511430.

The product of its digits is 259200, while the sum is 44.

The square root of 155666681 is about 12476.6454225485. The cubic root of 155666681 is about 537.9375846020.

The spelling of 155666681 in words is "one hundred fifty-five million, six hundred sixty-six thousand, six hundred eighty-one".