121621905 has 20 divisors (see below), whose sum is σ = 218019252. Its totient is φ = 64864800.

The previous prime is 121621889. The next prime is 121621937. The reversal of 121621905 is 509126121.

It can be written as a sum of positive squares in 2 ways, for example, as 36687249 + 84934656 = 6057^2 + 9216^2 .

It is not a de Polignac number, because 121621905 - 2⁴ = 121621889 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 149746 + ... + 150555.

Almost surely, 2^121621905 is an apocalyptic number.

121621905 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

121621905 is a deficient number, since it is larger than the sum of its proper divisors (96397347).

121621905 is an equidigital number, since it uses as much as digits as its factorization.

121621905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 300318 (or 300309 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 27.

The square root of 121621905 is about 11028.2321792752. The cubic root of 121621905 is about 495.4546786491.

The spelling of 121621905 in words is "one hundred twenty-one million, six hundred twenty-one thousand, nine hundred five".