121651891 has 4 divisors (see below), whose sum is σ = 121695912. Its totient is φ = 121607872.

The previous prime is 121651883. The next prime is 121651931. The reversal of 121651891 is 198156121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 198156121 = 61 ⋅3248461.

It is a cyclic number.

It is not a de Polignac number, because 121651891 - 2³ = 121651883 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (121651811) 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, 17566 + ... + 23491.

It is an arithmetic number, because the mean of its divisors is an integer number (30423978).

Almost surely, 2^121651891 is an apocalyptic number.

121651891 is a deficient number, since it is larger than the sum of its proper divisors (44021).

121651891 is an equidigital number, since it uses as much as digits as its factorization.

121651891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44020.

The product of its digits is 4320, while the sum is 34.

The square root of 121651891 is about 11029.5916062201. The cubic root of 121651891 is about 495.4953935822.

It can be divided in two parts, 1216518 and 91, that added together give a square (1216609 = 1103²).

The spelling of 121651891 in words is "one hundred twenty-one million, six hundred fifty-one thousand, eight hundred ninety-one".