21273813 has 32 divisors (see below), whose sum is σ = 34836480. Its totient is φ = 12723120.

The previous prime is 21273809. The next prime is 21273821. The reversal of 21273813 is 31837212.

It is not a de Polignac number, because 21273813 - 2² = 21273809 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21273803) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 24220 + ... + 25082.

It is an arithmetic number, because the mean of its divisors is an integer number (1088640).

Almost surely, 2^21273813 is an apocalyptic number.

It is an amenable number.

21273813 is a deficient number, since it is larger than the sum of its proper divisors (13562667).

21273813 is a wasteful number, since it uses less digits than its factorization.

21273813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 966 (or 960 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 21273813 is about 4612.3543879455. The cubic root of 21273813 is about 277.0863376512.

The spelling of 21273813 in words is "twenty-one million, two hundred seventy-three thousand, eight hundred thirteen".