891521 has 2 divisors, whose sum is σ = 891522. Its totient is φ = 891520.

The previous prime is 891509. The next prime is 891523. The reversal of 891521 is 125198.

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., 883600 + 7921 = 940^2 + 89^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-891521 is a prime.

It is a Sophie Germain prime.

Together with 891523, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (891523) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 445760 + 445761.

It is an arithmetic number, because the mean of its divisors is an integer number (445761).

2⁸⁹¹⁵²¹ is an apocalyptic number.

It is an amenable number.

891521 is a deficient number, since it is larger than the sum of its proper divisors (1).

891521 is an equidigital number, since it uses as much as digits as its factorization.

891521 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 891521 is about 944.2038974713. The cubic root of 891521 is about 96.2447818614.

The spelling of 891521 in words is "eight hundred ninety-one thousand, five hundred twenty-one".