20516987 has 4 divisors (see below), whose sum is σ = 20530560. Its totient is φ = 20503416.

The previous prime is 20516953. The next prime is 20516999. The reversal of 20516987 is 78961502.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20516987 - 2¹⁶ = 20451451 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20516987.

It is not an unprimeable number, because it can be changed into a prime (20516387) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4187 + ... + 7652.

It is an arithmetic number, because the mean of its divisors is an integer number (5132640).

Almost surely, 2^20516987 is an apocalyptic number.

20516987 is a deficient number, since it is larger than the sum of its proper divisors (13573).

20516987 is a wasteful number, since it uses less digits than its factorization.

20516987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13572.

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 20516987 is about 4529.5680809543. The cubic root of 20516987 is about 273.7607578322.

The spelling of 20516987 in words is "twenty million, five hundred sixteen thousand, nine hundred eighty-seven".