181533993 has 12 divisors (see below), whose sum is σ = 243505584. Its totient is φ = 120295000.

The previous prime is 181533983. The next prime is 181534013. The reversal of 181533993 is 399335181.

It is a happy number.

It is not a de Polignac number, because 181533993 - 2⁴ = 181533977 is a prime.

It is a super-2 number, since 2×181533993² = 65909181229048098, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (181533983) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 369478 + ... + 369968.

It is an arithmetic number, because the mean of its divisors is an integer number (20292132).

Almost surely, 2^181533993 is an apocalyptic number.

It is an amenable number.

181533993 is a deficient number, since it is larger than the sum of its proper divisors (61971591).

181533993 is an frugal number, since it uses more digits than its factorization.

181533993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1236 (or 745 counting only the distinct ones).

The product of its digits is 87480, while the sum is 42.

The square root of 181533993 is about 13473.4551248000. The cubic root of 181533993 is about 566.2210187449.

The spelling of 181533993 in words is "one hundred eighty-one million, five hundred thirty-three thousand, nine hundred ninety-three".