921581 has 2 divisors, whose sum is σ = 921582. Its totient is φ = 921580.

The previous prime is 921563. The next prime is 921589. The reversal of 921581 is 185129.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 885481 + 36100 = 941^2 + 190^2 .

It is a cyclic number.

It is not a de Polignac number, because 921581 - 2⁶ = 921517 is a prime.

It is a super-2 number, since 2×921581² = 1698623079122, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 921581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (921589) by changing a digit.

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 as a sum of consecutive naturals, namely, 460790 + 460791.

It is an arithmetic number, because the mean of its divisors is an integer number (460791).

2⁹²¹⁵⁸¹ is an apocalyptic number.

It is an amenable number.

921581 is a deficient number, since it is larger than the sum of its proper divisors (1).

921581 is an equidigital number, since it uses as much as digits as its factorization.

921581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 720, while the sum is 26.

The square root of 921581 is about 959.9901041157. The cubic root of 921581 is about 97.3145631639.

The spelling of 921581 in words is "nine hundred twenty-one thousand, five hundred eighty-one".