2116821 has 8 divisors (see below), whose sum is σ = 3225664. Its totient is φ = 1209600.

The previous prime is 2116817. The next prime is 2116837. The reversal of 2116821 is 1286112.

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

It is not a de Polignac number, because 2116821 - 2² = 2116817 is a prime.

It is a super-2 number, since 2×2116821² = 8961862292082, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 100801 = 2116821 / (2 + 1 + 1 + 6 + 8 + 2 + 1).

It is a Duffinian number.

2116821 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2116801) 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, 50380 + ... + 50421.

It is an arithmetic number, because the mean of its divisors is an integer number (403208).

2^2116821 is an apocalyptic number.

2116821 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

2116821 is a deficient number, since it is larger than the sum of its proper divisors (1108843).

2116821 is a wasteful number, since it uses less digits than its factorization.

2116821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100811.

The product of its digits is 192, while the sum is 21.

The square root of 2116821 is about 1454.9298952183. The cubic root of 2116821 is about 128.3989222646.

The spelling of 2116821 in words is "two million, one hundred sixteen thousand, eight hundred twenty-one".