221981581 has 4 divisors (see below), whose sum is σ = 222013372. Its totient is φ = 221949792.

The previous prime is 221981567. The next prime is 221981587. The reversal of 221981581 is 185189122.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 57244356 + 164737225 = 7566^2 + 12835^2 .

It is a cyclic number.

It is not a de Polignac number, because 221981581 - 2⁵ = 221981549 is a prime.

It is a super-2 number, since 2×221981581² = 98551644606519122, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 221981581.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221981587) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 360 + ... + 21073.

It is an arithmetic number, because the mean of its divisors is an integer number (55503343).

Almost surely, 2^221981581 is an apocalyptic number.

It is an amenable number.

221981581 is a deficient number, since it is larger than the sum of its proper divisors (31791).

221981581 is a wasteful number, since it uses less digits than its factorization.

221981581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31790.

The product of its digits is 11520, while the sum is 37.

The square root of 221981581 is about 14899.0463117610. The cubic root of 221981581 is about 605.4881482500.

The spelling of 221981581 in words is "two hundred twenty-one million, nine hundred eighty-one thousand, five hundred eighty-one".