117821 has 4 divisors (see below), whose sum is σ = 128544. Its totient is φ = 107100.

The previous prime is 117811. The next prime is 117833. The reversal of 117821 is 128711.

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: 128711 = 11 ⋅11701.

It is a cyclic number.

It is not a de Polignac number, because 117821 - 2⁶ = 117757 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 117793 and 117802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (117811) 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, 5345 + ... + 5366.

It is an arithmetic number, because the mean of its divisors is an integer number (32136).

2¹¹⁷⁸²¹ is an apocalyptic number.

117821 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

117821 is a deficient number, since it is larger than the sum of its proper divisors (10723).

117821 is a wasteful number, since it uses less digits than its factorization.

117821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10722.

The product of its digits is 112, while the sum is 20.

The square root of 117821 is about 343.2506372900. The cubic root of 117821 is about 49.0238673120.

The spelling of 117821 in words is "one hundred seventeen thousand, eight hundred twenty-one".