20756987 has 4 divisors (see below), whose sum is σ = 21849480. Its totient is φ = 19664496.

The previous prime is 20756977. The next prime is 20756993. The reversal of 20756987 is 78965702.

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 20756987 - 2¹² = 20752891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20756977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 546218 + ... + 546255.

It is an arithmetic number, because the mean of its divisors is an integer number (5462370).

Almost surely, 2^20756987 is an apocalyptic number.

20756987 is a deficient number, since it is larger than the sum of its proper divisors (1092493).

20756987 is a wasteful number, since it uses less digits than its factorization.

20756987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1092492.

The product of its (nonzero) digits is 211680, while the sum is 44.

The square root of 20756987 is about 4555.9836479074. The cubic root of 20756987 is about 274.8240726009.

The spelling of 20756987 in words is "twenty million, seven hundred fifty-six thousand, nine hundred eighty-seven".