121638787 has 4 divisors (see below), whose sum is σ = 124467640. Its totient is φ = 118809936.

The previous prime is 121638709. The next prime is 121638799. The reversal of 121638787 is 787836121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 787836121 = 19 ⋅41465059.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-121638787 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (43), and also a Moran number because the ratio is a prime number: 2828809 = 121638787 / (1 + 2 + 1 + 6 + 3 + 8 + 7 + 8 + 7).

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (121638287) 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 3 ways as a sum of consecutive naturals, for example, 1414362 + ... + 1414447.

It is an arithmetic number, because the mean of its divisors is an integer number (31116910).

Almost surely, 2^121638787 is an apocalyptic number.

121638787 is a deficient number, since it is larger than the sum of its proper divisors (2828853).

121638787 is an equidigital number, since it uses as much as digits as its factorization.

121638787 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2828852.

The product of its digits is 112896, while the sum is 43.

The square root of 121638787 is about 11028.9975519083. The cubic root of 121638787 is about 495.4776018194.

The spelling of 121638787 in words is "one hundred twenty-one million, six hundred thirty-eight thousand, seven hundred eighty-seven".