20805513 has 12 divisors (see below), whose sum is σ = 29279088. Its totient is φ = 13139640.

The previous prime is 20805509. The next prime is 20805517. The reversal of 20805513 is 31550802.

It is an interprime number because it is at equal distance from previous prime (20805509) and next prime (20805517).

It is not a de Polignac number, because 20805513 - 2² = 20805509 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20805517) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8523 + ... + 10688.

It is an arithmetic number, because the mean of its divisors is an integer number (2439924).

Almost surely, 2^20805513 is an apocalyptic number.

It is an amenable number.

20805513 is a deficient number, since it is larger than the sum of its proper divisors (8473575).

20805513 is a wasteful number, since it uses less digits than its factorization.

20805513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19252 (or 19233 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 24.

The square root of 20805513 is about 4561.3060629605. The cubic root of 20805513 is about 275.0380685591.

The spelling of 20805513 in words is "twenty million, eight hundred five thousand, five hundred thirteen".