438121991 has 4 divisors (see below), whose sum is σ = 443044800. Its totient is φ = 433199184.

The previous prime is 438121987. The next prime is 438122017. The reversal of 438121991 is 199121834.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 438121991 - 2² = 438121987 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 (438121951) 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, 2461271 + ... + 2461448.

It is an arithmetic number, because the mean of its divisors is an integer number (110761200).

Almost surely, 2^438121991 is an apocalyptic number.

438121991 is a deficient number, since it is larger than the sum of its proper divisors (4922809).

438121991 is an equidigital number, since it uses as much as digits as its factorization.

438121991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4922808.

The product of its digits is 15552, while the sum is 38.

The square root of 438121991 is about 20931.3638112761. The cubic root of 438121991 is about 759.5068309026.

The spelling of 438121991 in words is "four hundred thirty-eight million, one hundred twenty-one thousand, nine hundred ninety-one".