21427813 has 4 divisors (see below), whose sum is σ = 23375808. Its totient is φ = 19479820.

The previous prime is 21427807. The next prime is 21427829. The reversal of 21427813 is 31872412.

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 21427813 - 2¹³ = 21419621 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 (21427843) 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, 973981 + ... + 974002.

It is an arithmetic number, because the mean of its divisors is an integer number (5843952).

Almost surely, 2^21427813 is an apocalyptic number.

It is an amenable number.

21427813 is a deficient number, since it is larger than the sum of its proper divisors (1947995).

21427813 is a wasteful number, since it uses less digits than its factorization.

21427813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1947994.

The product of its digits is 2688, while the sum is 28.

The square root of 21427813 is about 4629.0185784894. The cubic root of 21427813 is about 277.7533351945.

The spelling of 21427813 in words is "twenty-one million, four hundred twenty-seven thousand, eight hundred thirteen".