121991440 has 40 divisors (see below), whose sum is σ = 285135768. Its totient is φ = 48537600.

The previous prime is 121991423. The next prime is 121991447. The reversal of 121991440 is 44199121.

It can be written as a sum of positive squares in 4 ways, for example, as 9461776 + 112529664 = 3076^2 + 10608^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×121991440² = 29763822866547200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (121991447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11490 + ... + 19390.

Almost surely, 2^121991440 is an apocalyptic number.

121991440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

121991440 is an abundant number, since it is smaller than the sum of its proper divisors (163144328).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

121991440 is a wasteful number, since it uses less digits than its factorization.

121991440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8107 (or 8101 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 121991440 is about 11044.9735173970. The cubic root of 121991440 is about 495.9559664343.

The spelling of 121991440 in words is "one hundred twenty-one million, nine hundred ninety-one thousand, four hundred forty".