261721151999 has 8 divisors (see below), whose sum is σ = 264016843440. Its totient is φ = 259433418816.

The previous prime is 261721151969. The next prime is 261721152001. The reversal of 261721151999 is 999151127162.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 261721151999 - 2²⁰ = 261720103423 is a prime.

It is a super-2 number, since 2×261721151999² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 261721151999.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261721151929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1923494 + ... + 2055059.

It is an arithmetic number, because the mean of its divisors is an integer number (33002105430).

Almost surely, 2^261721151999 is an apocalyptic number.

261721151999 is a deficient number, since it is larger than the sum of its proper divisors (2295691441).

261721151999 is a wasteful number, since it uses less digits than its factorization.

261721151999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3979129.

The product of its digits is 612360, while the sum is 53.

The spelling of 261721151999 in words is "two hundred sixty-one billion, seven hundred twenty-one million, one hundred fifty-one thousand, nine hundred ninety-nine".