164531781 has 6 divisors (see below), whose sum is σ = 237657030. Its totient is φ = 109687848.

The previous prime is 164531771. The next prime is 164531789. The reversal of 164531781 is 187135461.

164531781 is a `hidden beast` number, since 1 + 645 + 3 + 1 + 7 + 8 + 1 = 666.

164531781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 149670756 + 14861025 = 12234^2 + 3855^2 .

It is not a de Polignac number, because 164531781 - 2⁵ = 164531749 is a prime.

It is a super-2 number, since 2×164531781² = 54141413918063922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (164531789) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9140646 + ... + 9140663.

It is an arithmetic number, because the mean of its divisors is an integer number (39609505).

Almost surely, 2^164531781 is an apocalyptic number.

It is an amenable number.

164531781 is a deficient number, since it is larger than the sum of its proper divisors (73125249).

164531781 is a wasteful number, since it uses less digits than its factorization.

164531781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18281315 (or 18281312 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 164531781 is about 12826.9942309179. The cubic root of 164531781 is about 547.9613575412.

The spelling of 164531781 in words is "one hundred sixty-four million, five hundred thirty-one thousand, seven hundred eighty-one".