171221840 has 20 divisors (see below), whose sum is σ = 398090964. Its totient is φ = 68488704.

The previous prime is 171221839. The next prime is 171221857. The reversal of 171221840 is 48122171.

It can be written as a sum of positive squares in 2 ways, for example, as 123832384 + 47389456 = 11128^2 + 6884^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a hoax number, since the sum of its digits (26) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1070057 + ... + 1070216.

Almost surely, 2^171221840 is an apocalyptic number.

171221840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

171221840 is an abundant number, since it is smaller than the sum of its proper divisors (226869124).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

171221840 is a wasteful number, since it uses less digits than its factorization.

171221840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2140286 (or 2140280 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 26.

The square root of 171221840 is about 13085.1763457739. The cubic root of 171221840 is about 555.2898304930.

The spelling of 171221840 in words is "one hundred seventy-one million, two hundred twenty-one thousand, eight hundred forty".