10421821 has 4 divisors (see below), whose sum is σ = 10442272. Its totient is φ = 10401372.

The previous prime is 10421791. The next prime is 10421837. The reversal of 10421821 is 12812401.

It is a happy number.

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: 12812401 = 7 ⋅1830343.

It is a cyclic number.

It is not a de Polignac number, because 10421821 - 2¹⁹ = 9897533 is a prime.

It is a super-2 number, since 2×10421821² = 217228705912082, which contains 22 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 (10421881) 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, 9441 + ... + 10486.

It is an arithmetic number, because the mean of its divisors is an integer number (2610568).

Almost surely, 2^10421821 is an apocalyptic number.

It is an amenable number.

10421821 is a deficient number, since it is larger than the sum of its proper divisors (20451).

10421821 is an equidigital number, since it uses as much as digits as its factorization.

10421821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20450.

The product of its (nonzero) digits is 128, while the sum is 19.

The square root of 10421821 is about 3228.2845289720. The cubic root of 10421821 is about 218.4311320436.

The spelling of 10421821 in words is "ten million, four hundred twenty-one thousand, eight hundred twenty-one".