21051823 has 6 divisors (see below), whose sum is σ = 22795944. Its totient is φ = 19432296.

The previous prime is 21051809. The next prime is 21051839. The reversal of 21051823 is 32815012.

It is not a de Polignac number, because 21051823 - 2⁹ = 21051311 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21051794 and 21051803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21051323) 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 5 ways as a sum of consecutive naturals, for example, 62115 + ... + 62452.

It is an arithmetic number, because the mean of its divisors is an integer number (3799324).

Almost surely, 2^21051823 is an apocalyptic number.

21051823 is a deficient number, since it is larger than the sum of its proper divisors (1744121).

21051823 is a wasteful number, since it uses less digits than its factorization.

21051823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124593 (or 124580 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21051823 is about 4588.2265637172. The cubic root of 21051823 is about 276.1191768104.

Adding to 21051823 its reverse (32815012), we get a palindrome (53866835).

The spelling of 21051823 in words is "twenty-one million, fifty-one thousand, eight hundred twenty-three".