381555981 has 16 divisors (see below), whose sum is σ = 570760320. Its totient is φ = 251899200.

The previous prime is 381555961. The next prime is 381555989. The reversal of 381555981 is 189555183.

381555981 is a `hidden beast` number, since 3 + 8 + 1 + 55 + 598 + 1 = 666.

It is not a de Polignac number, because 381555981 - 2⁵ = 381555949 is a prime.

It is a super-2 number, since 2×381555981² = 291169933273744722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (381555989) 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, 65820 + ... + 71381.

It is an arithmetic number, because the mean of its divisors is an integer number (35672520).

Almost surely, 2^381555981 is an apocalyptic number.

It is an amenable number.

381555981 is a deficient number, since it is larger than the sum of its proper divisors (189204339).

381555981 is a wasteful number, since it uses less digits than its factorization.

381555981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137313 (or 137307 counting only the distinct ones).

The product of its digits is 216000, while the sum is 45.

The square root of 381555981 is about 19533.4579887945. The cubic root of 381555981 is about 725.3029132949.

The spelling of 381555981 in words is "three hundred eighty-one million, five hundred fifty-five thousand, nine hundred eighty-one".