20987785 has 32 divisors (see below), whose sum is σ = 31288320. Its totient is φ = 13160448.

The previous prime is 20987783. The next prime is 20987797. The reversal of 20987785 is 58778902.

It is not a de Polignac number, because 20987785 - 2¹ = 20987783 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20987783) 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 31 ways as a sum of consecutive naturals, for example, 87696 + ... + 87934.

It is an arithmetic number, because the mean of its divisors is an integer number (977760).

Almost surely, 2^20987785 is an apocalyptic number.

It is an amenable number.

20987785 is a deficient number, since it is larger than the sum of its proper divisors (10300535).

20987785 is a wasteful number, since it uses less digits than its factorization.

20987785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 457.

The product of its (nonzero) digits is 282240, while the sum is 46.

The square root of 20987785 is about 4581.2427353285. The cubic root of 20987785 is about 275.8389147889.

The spelling of 20987785 in words is "twenty million, nine hundred eighty-seven thousand, seven hundred eighty-five".