121978139 has 4 divisors (see below), whose sum is σ = 122616960. Its totient is φ = 121339320.

The previous prime is 121978121. The next prime is 121978141. The reversal of 121978139 is 931879121.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 931879121 = 619 ⋅1505459.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-121978139 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 121978096 and 121978105.

It is not an unprimeable number, because it can be changed into a prime (121978169) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 319124 + ... + 319505.

It is an arithmetic number, because the mean of its divisors is an integer number (30654240).

Almost surely, 2^121978139 is an apocalyptic number.

121978139 is a deficient number, since it is larger than the sum of its proper divisors (638821).

121978139 is an equidigital number, since it uses as much as digits as its factorization.

121978139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 638820.

The product of its digits is 27216, while the sum is 41.

The square root of 121978139 is about 11044.3713718799. The cubic root of 121978139 is about 495.9379407158.

The spelling of 121978139 in words is "one hundred twenty-one million, nine hundred seventy-eight thousand, one hundred thirty-nine".