20987786 has 8 divisors (see below), whose sum is σ = 31513764. Its totient is φ = 10483200.

The previous prime is 20987783. The next prime is 20987797. The reversal of 20987786 is 68778902.

It can be written as a sum of positive squares in 2 ways, for example, as 16556761 + 4431025 = 4069^2 + 2105^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×20987786² = 880974322363592, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20987786.

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 3 ways as a sum of consecutive naturals, for example, 2615 + ... + 6986.

Almost surely, 2^20987786 is an apocalyptic number.

20987786 is a deficient number, since it is larger than the sum of its proper divisors (10525978).

20987786 is a wasteful number, since it uses less digits than its factorization.

20987786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10696.

The product of its (nonzero) digits is 338688, while the sum is 47.

The square root of 20987786 is about 4581.2428444692. The cubic root of 20987786 is about 275.8389191698.

The spelling of 20987786 in words is "twenty million, nine hundred eighty-seven thousand, seven hundred eighty-six".