21269821 has 4 divisors (see below), whose sum is σ = 21764512. Its totient is φ = 20775132.

The previous prime is 21269819. The next prime is 21269827. The reversal of 21269821 is 12896212.

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.

It is a cyclic number.

It is not a de Polignac number, because 21269821 - 2¹ = 21269819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21269827) 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, 247281 + ... + 247366.

It is an arithmetic number, because the mean of its divisors is an integer number (5441128).

Almost surely, 2^21269821 is an apocalyptic number.

It is an amenable number.

21269821 is a deficient number, since it is larger than the sum of its proper divisors (494691).

21269821 is an equidigital number, since it uses as much as digits as its factorization.

21269821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 494690.

The product of its digits is 3456, while the sum is 31.

The square root of 21269821 is about 4611.9216168534. The cubic root of 21269821 is about 277.0690049512.

The spelling of 21269821 in words is "twenty-one million, two hundred sixty-nine thousand, eight hundred twenty-one".