121721565221 has 8 divisors (see below), whose sum is σ = 125027099160. Its totient is φ = 118416860928.

The previous prime is 121721565127. The next prime is 121721565227. The reversal of 121721565221 is 122565127121.

It can be written as a sum of positive squares in 4 ways, for example, as 5478072196 + 116243493025 = 74014^2 + 340945^2 .

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 121721565221 - 2²² = 121717370917 is a prime.

It is a super-2 number, since 2×121721565221² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121721565227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 95945 + ... + 502641.

It is an arithmetic number, because the mean of its divisors is an integer number (15628387395).

Almost surely, 2^121721565221 is an apocalyptic number.

It is an amenable number.

121721565221 is a deficient number, since it is larger than the sum of its proper divisors (3305533939).

121721565221 is an equidigital number, since it uses as much as digits as its factorization.

121721565221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 414823.

The product of its digits is 16800, while the sum is 35.

The spelling of 121721565221 in words is "one hundred twenty-one billion, seven hundred twenty-one million, five hundred sixty-five thousand, two hundred twenty-one".