261629521 has 2 divisors, whose sum is σ = 261629522. Its totient is φ = 261629520.

The previous prime is 261629519. The next prime is 261629567. The reversal of 261629521 is 125926162.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 170694225 + 90935296 = 13065^2 + 9536^2 .

It is a cyclic number.

It is not a de Polignac number, because 261629521 - 2¹ = 261629519 is a prime.

Together with 261629519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (261729521) 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, 130814760 + 130814761.

It is an arithmetic number, because the mean of its divisors is an integer number (130814761).

Almost surely, 2^261629521 is an apocalyptic number.

It is an amenable number.

261629521 is a deficient number, since it is larger than the sum of its proper divisors (1).

261629521 is an equidigital number, since it uses as much as digits as its factorization.

261629521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12960, while the sum is 34.

The square root of 261629521 is about 16174.9658732252. The cubic root of 261629521 is about 639.5810417184.

The spelling of 261629521 in words is "two hundred sixty-one million, six hundred twenty-nine thousand, five hundred twenty-one".