121856591 has 4 divisors (see below), whose sum is σ = 122121384. Its totient is φ = 121591800.

The previous prime is 121856587. The next prime is 121856597. The reversal of 121856591 is 195658121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 195658121 = 12433 ⋅15737.

It is a cyclic number.

It is not a de Polignac number, because 121856591 - 2² = 121856587 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121856597) 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, 131705 + ... + 132626.

It is an arithmetic number, because the mean of its divisors is an integer number (30530346).

Almost surely, 2^121856591 is an apocalyptic number.

121856591 is a deficient number, since it is larger than the sum of its proper divisors (264793).

121856591 is an equidigital number, since it uses as much as digits as its factorization.

121856591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 264792.

The product of its digits is 21600, while the sum is 38.

The square root of 121856591 is about 11038.8672879059. The cubic root of 121856591 is about 495.7731562745.

The spelling of 121856591 in words is "one hundred twenty-one million, eight hundred fifty-six thousand, five hundred ninety-one".