261721151969 has 2 divisors, whose sum is σ = 261721151970. Its totient is φ = 261721151968.

The previous prime is 261721151941. The next prime is 261721152001. The reversal of 261721151969 is 969151127162.

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., 234171791569 + 27549360400 = 483913^2 + 165980^2 .

It is a cyclic number.

It is not a de Polignac number, because 261721151969 - 2¹² = 261721147873 is a prime.

It is a super-2 number, since 2×261721151969² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (261721151929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130860575984 + 130860575985.

It is an arithmetic number, because the mean of its divisors is an integer number (130860575985).

Almost surely, 2^261721151969 is an apocalyptic number.

It is an amenable number.

261721151969 is a deficient number, since it is larger than the sum of its proper divisors (1).

261721151969 is an equidigital number, since it uses as much as digits as its factorization.

261721151969 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 408240, while the sum is 50.

The spelling of 261721151969 in words is "two hundred sixty-one billion, seven hundred twenty-one million, one hundred fifty-one thousand, nine hundred sixty-nine".