20516815 has 16 divisors (see below), whose sum is σ = 26990496. Its totient is φ = 14848000.

The previous prime is 20516803. The next prime is 20516831. The reversal of 20516815 is 51861502.

It is not a de Polignac number, because 20516815 - 2²¹ = 18419663 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12015 + ... + 13615.

It is an arithmetic number, because the mean of its divisors is an integer number (1686906).

Almost surely, 2^20516815 is an apocalyptic number.

20516815 is a deficient number, since it is larger than the sum of its proper divisors (6473681).

20516815 is a wasteful number, since it uses less digits than its factorization.

20516815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1850.

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 20516815 is about 4529.5490945568. The cubic root of 20516815 is about 273.7599928241.

It can be divided in two parts, 205 and 16815, that added together give a triangular number (17020 = T₁₈₄).

The spelling of 20516815 in words is "twenty million, five hundred sixteen thousand, eight hundred fifteen".