21079381 has 4 divisors (see below), whose sum is σ = 21649132. Its totient is φ = 20509632.

The previous prime is 21079369. The next prime is 21079391. The reversal of 21079381 is 18397012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19945156 + 1134225 = 4466^2 + 1065^2 .

It is a cyclic number.

It is not a de Polignac number, because 21079381 - 2¹¹ = 21077333 is a prime.

It is a super-2 number, since 2×21079381² = 888680606686322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21079391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 284820 + ... + 284893.

It is an arithmetic number, because the mean of its divisors is an integer number (5412283).

Almost surely, 2^21079381 is an apocalyptic number.

It is an amenable number.

21079381 is a deficient number, since it is larger than the sum of its proper divisors (569751).

21079381 is an equidigital number, since it uses as much as digits as its factorization.

21079381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 569750.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 21079381 is about 4591.2287026459. The cubic root of 21079381 is about 276.2396093633.

The spelling of 21079381 in words is "twenty-one million, seventy-nine thousand, three hundred eighty-one".