181221645 has 16 divisors (see below), whose sum is σ = 316314432. Its totient is φ = 87864960.

The previous prime is 181221643. The next prime is 181221653. The reversal of 181221645 is 546122181.

181221645 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 181221645 - 2¹ = 181221643 is a prime.

It is a super-3 number, since 3×181221645³ (a number of 26 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181221643) 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, 548992 + ... + 549321.

It is an arithmetic number, because the mean of its divisors is an integer number (19769652).

Almost surely, 2^181221645 is an apocalyptic number.

181221645 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

181221645 is a deficient number, since it is larger than the sum of its proper divisors (135092787).

181221645 is a wasteful number, since it uses less digits than its factorization.

181221645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1098332.

The product of its digits is 3840, while the sum is 30.

The square root of 181221645 is about 13461.8588983840. The cubic root of 181221645 is about 565.8960850487.

The spelling of 181221645 in words is "one hundred eighty-one million, two hundred twenty-one thousand, six hundred forty-five".