21137005 has 4 divisors (see below), whose sum is σ = 25364412. Its totient is φ = 16909600.

The previous prime is 21136963. The next prime is 21137021. The reversal of 21137005 is 50073112.

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 9753129 + 11383876 = 3123^2 + 3374^2 .

It is not a de Polignac number, because 21137005 - 2¹⁹ = 20612717 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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, 2113696 + ... + 2113705.

It is an arithmetic number, because the mean of its divisors is an integer number (6341103).

Almost surely, 2^21137005 is an apocalyptic number.

It is an amenable number.

21137005 is a deficient number, since it is larger than the sum of its proper divisors (4227407).

21137005 is an equidigital number, since it uses as much as digits as its factorization.

21137005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4227406.

The product of its (nonzero) digits is 210, while the sum is 19.

The square root of 21137005 is about 4597.4998640566. The cubic root of 21137005 is about 276.4910960076.

It can be divided in two parts, 21 and 137005, that added together give a triangular number (137026 = T₅₂₃).

The spelling of 21137005 in words is "twenty-one million, one hundred thirty-seven thousand, five".