117851821 has 4 divisors (see below), whose sum is σ = 117924352. Its totient is φ = 117779292.

The previous prime is 117851819. The next prime is 117851827. The reversal of 117851821 is 128158711.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 128158711 = 5077 ⋅25243.

It is a cyclic number.

It is not a de Polignac number, because 117851821 - 2¹ = 117851819 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 (117851827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33771 + ... + 37096.

It is an arithmetic number, because the mean of its divisors is an integer number (29481088).

Almost surely, 2^117851821 is an apocalyptic number.

It is an amenable number.

117851821 is a deficient number, since it is larger than the sum of its proper divisors (72531).

117851821 is an equidigital number, since it uses as much as digits as its factorization.

117851821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72530.

The product of its digits is 4480, while the sum is 34.

The square root of 117851821 is about 10855.9578573242. The cubic root of 117851821 is about 490.2814168547.

The spelling of 117851821 in words is "one hundred seventeen million, eight hundred fifty-one thousand, eight hundred twenty-one".