221531540 has 12 divisors (see below), whose sum is σ = 465216276. Its totient is φ = 88612608.

The previous prime is 221531533. The next prime is 221531587. The reversal of 221531540 is 45135122.

It can be written as a sum of positive squares in 2 ways, for example, as 25867396 + 195664144 = 5086^2 + 13988^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5538269 + ... + 5538308.

It is an arithmetic number, because the mean of its divisors is an integer number (38768023).

Almost surely, 2^221531540 is an apocalyptic number.

221531540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

221531540 is an abundant number, since it is smaller than the sum of its proper divisors (243684736).

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

221531540 is a wasteful number, since it uses less digits than its factorization.

221531540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11076586 (or 11076584 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 221531540 is about 14883.9356354427. The cubic root of 221531540 is about 605.0786865759.

Adding to 221531540 its reverse (45135122), we get a palindrome (266666662).

The spelling of 221531540 in words is "two hundred twenty-one million, five hundred thirty-one thousand, five hundred forty".