21340605 has 32 divisors (see below), whose sum is σ = 40118400. Its totient is φ = 9550080.

The previous prime is 21340603. The next prime is 21340633. The reversal of 21340605 is 50604312.

It is a happy number.

It is not a de Polignac number, because 21340605 - 2¹ = 21340603 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21340603) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2830 + ... + 7119.

It is an arithmetic number, because the mean of its divisors is an integer number (1253700).

Almost surely, 2^21340605 is an apocalyptic number.

It is an amenable number.

21340605 is a deficient number, since it is larger than the sum of its proper divisors (18777795).

21340605 is a wasteful number, since it uses less digits than its factorization.

21340605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9981.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21340605 is about 4619.5892674566. The cubic root of 21340605 is about 277.3760179860.

Adding to 21340605 its reverse (50604312), we get a palindrome (71944917).

It can be divided in two parts, 21340 and 605, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21340605 in words is "twenty-one million, three hundred forty thousand, six hundred five".