121591987 has 4 divisors (see below), whose sum is σ = 132645816. Its totient is φ = 110538160.

The previous prime is 121591913. The next prime is 121591991. The reversal of 121591987 is 789195121.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 121591987 - 2⁷ = 121591859 is a prime.

It is a super-2 number, since 2×121591987² = 29569222605216338, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (121591907) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 5526898 + ... + 5526919.

It is an arithmetic number, because the mean of its divisors is an integer number (33161454).

Almost surely, 2^121591987 is an apocalyptic number.

121591987 is a deficient number, since it is larger than the sum of its proper divisors (11053829).

121591987 is a wasteful number, since it uses less digits than its factorization.

121591987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11053828.

The product of its digits is 45360, while the sum is 43.

The square root of 121591987 is about 11026.8756681120. The cubic root of 121591987 is about 495.4140493762.

The spelling of 121591987 in words is "one hundred twenty-one million, five hundred ninety-one thousand, nine hundred eighty-seven".