23121991 has 8 divisors (see below), whose sum is σ = 23784768. Its totient is φ = 22464000.

The previous prime is 23121971. The next prime is 23122007. The reversal of 23121991 is 19912132.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 23121991 - 2¹³ = 23113799 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 (23121911) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10071 + ... + 12151.

It is an arithmetic number, because the mean of its divisors is an integer number (2973096).

Almost surely, 2^23121991 is an apocalyptic number.

23121991 is a deficient number, since it is larger than the sum of its proper divisors (662777).

23121991 is a wasteful number, since it uses less digits than its factorization.

23121991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2393.

The product of its digits is 972, while the sum is 28.

The square root of 23121991 is about 4808.5331443175. The cubic root of 23121991 is about 284.8886032276. Note that the first 3 decimals are identical.

It can be divided in two parts, 231 and 21991, that added together give a palindrome (22222).

The spelling of 23121991 in words is "twenty-three million, one hundred twenty-one thousand, nine hundred ninety-one".