999731521 has 2 divisors, whose sum is σ = 999731522. Its totient is φ = 999731520.

The previous prime is 999731519. The next prime is 999731533. The reversal of 999731521 is 125137999.

999731521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 985960000 + 13771521 = 31400^2 + 3711^2 .

It is a cyclic number.

It is not a de Polignac number, because 999731521 - 2¹ = 999731519 is a prime.

It is a super-2 number, since 2×999731521² = 1998926228161946882, which contains 22 as substring.

Together with 999731519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (999731591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499865760 + 499865761.

It is an arithmetic number, because the mean of its divisors is an integer number (499865761).

Almost surely, 2^999731521 is an apocalyptic number.

It is an amenable number.

999731521 is a deficient number, since it is larger than the sum of its proper divisors (1).

999731521 is an equidigital number, since it uses as much as digits as its factorization.

999731521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 153090, while the sum is 46.

The square root of 999731521 is about 31618.5312910009. The cubic root of 999731521 is about 999.9104989898.

The spelling of 999731521 in words is "nine hundred ninety-nine million, seven hundred thirty-one thousand, five hundred twenty-one".