121990221 has 18 divisors (see below), whose sum is σ = 181117482. Its totient is φ = 79120800.

The previous prime is 121990217. The next prime is 121990243. The reversal of 121990221 is 122099121.

It can be written as a sum of positive squares in 3 ways, for example, as 100701225 + 21288996 = 10035^2 + 4614^2 .

It is not a de Polignac number, because 121990221 - 2² = 121990217 is a prime.

It is a super-2 number, since 2×121990221² = 29763228039257682, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121990201) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 7371 + ... + 17271.

Almost surely, 2^121990221 is an apocalyptic number.

It is an amenable number.

121990221 is a deficient number, since it is larger than the sum of its proper divisors (59127261).

121990221 is an equidigital number, since it uses as much as digits as its factorization.

121990221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9981 (or 9941 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 27.

The square root of 121990221 is about 11044.9183337859. The cubic root of 121990221 is about 495.9543144814.

Subtracting 121990221 from its reverse (122099121), we obtain a square (108900 = 330²).

The spelling of 121990221 in words is "one hundred twenty-one million, nine hundred ninety thousand, two hundred twenty-one".