21168513 has 16 divisors (see below), whose sum is σ = 32091840. Its totient is φ = 13783392.

The previous prime is 21168509. The next prime is 21168517. The reversal of 21168513 is 31586112.

It is an interprime number because it is at equal distance from previous prime (21168509) and next prime (21168517).

It is not a de Polignac number, because 21168513 - 2² = 21168509 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21168517) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7956 + ... + 10277.

It is an arithmetic number, because the mean of its divisors is an integer number (2005740).

Almost surely, 2^21168513 is an apocalyptic number.

It is an amenable number.

21168513 is a deficient number, since it is larger than the sum of its proper divisors (10923327).

21168513 is a wasteful number, since it uses less digits than its factorization.

21168513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18285 (or 18279 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 21168513 is about 4600.9252330374. The cubic root of 21168513 is about 276.6284121557.

The spelling of 21168513 in words is "twenty-one million, one hundred sixty-eight thousand, five hundred thirteen".