21310605 has 48 divisors (see below), whose sum is σ = 39677040. Its totient is φ = 10543104.

The previous prime is 21310603. The next prime is 21310607. The reversal of 21310605 is 50601312.

It is an interprime number because it is at equal distance from previous prime (21310603) and next prime (21310607).

It can be written as a sum of positive squares in 8 ways, for example, as 3896676 + 17413929 = 1974^2 + 4173^2 .

It is not a de Polignac number, because 21310605 - 2¹ = 21310603 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21310603) 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 47 ways as a sum of consecutive naturals, for example, 67929 + ... + 68241.

It is an arithmetic number, because the mean of its divisors is an integer number (826605).

Almost surely, 2^21310605 is an apocalyptic number.

It is an amenable number.

21310605 is a deficient number, since it is larger than the sum of its proper divisors (18366435).

21310605 is a wasteful number, since it uses less digits than its factorization.

21310605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 430 (or 427 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 21310605 is about 4616.3410835856. The cubic root of 21310605 is about 277.2459813280.

Adding to 21310605 its reverse (50601312), we get a palindrome (71911917).

The spelling of 21310605 in words is "twenty-one million, three hundred ten thousand, six hundred five".