21274381 has 4 divisors (see below), whose sum is σ = 21284064. Its totient is φ = 21264700.

The previous prime is 21274373. The next prime is 21274391. The reversal of 21274381 is 18347212.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21274381 - 2³ = 21274373 is a prime.

It is a super-2 number, since 2×21274381² = 905198573866322, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21274391) 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, 216 + ... + 6526.

It is an arithmetic number, because the mean of its divisors is an integer number (5321016).

Almost surely, 2^21274381 is an apocalyptic number.

It is an amenable number.

21274381 is a deficient number, since it is larger than the sum of its proper divisors (9683).

21274381 is an equidigital number, since it uses as much as digits as its factorization.

21274381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9682.

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

The square root of 21274381 is about 4612.4159612940. The cubic root of 21274381 is about 277.0888036508.

The spelling of 21274381 in words is "twenty-one million, two hundred seventy-four thousand, three hundred eighty-one".