11921821 has 4 divisors (see below), whose sum is σ = 11940732. Its totient is φ = 11902912.

The previous prime is 11921773. The next prime is 11921827. The reversal of 11921821 is 12812911.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12812911 = 223 ⋅57457.

It can be written as a sum of positive squares in 2 ways, for example, as 3189796 + 8732025 = 1786^2 + 2955^2 .

It is a cyclic number.

It is not a de Polignac number, because 11921821 - 2²¹ = 9824669 is a prime.

It is a super-3 number, since 3×11921821³ (a number of 22 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11921827) 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, 8476 + ... + 9781.

It is an arithmetic number, because the mean of its divisors is an integer number (2985183).

Almost surely, 2^11921821 is an apocalyptic number.

It is an amenable number.

11921821 is a deficient number, since it is larger than the sum of its proper divisors (18911).

11921821 is an equidigital number, since it uses as much as digits as its factorization.

11921821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18910.

The product of its digits is 288, while the sum is 25.

The square root of 11921821 is about 3452.7990094994. The cubic root of 11921821 is about 228.4445836946. Note that the first 3 decimals are identical.

The spelling of 11921821 in words is "eleven million, nine hundred twenty-one thousand, eight hundred twenty-one".