20977987 has 4 divisors (see below), whose sum is σ = 21143296. Its totient is φ = 20812680.

The previous prime is 20977967. The next prime is 20978011. The reversal of 20977987 is 78977902.

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 20977987 - 2¹¹ = 20975939 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 20977987.

It is not an unprimeable number, because it can be changed into a prime (20977967) 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, 82464 + ... + 82717.

It is an arithmetic number, because the mean of its divisors is an integer number (5285824).

Almost surely, 2^20977987 is an apocalyptic number.

20977987 is a deficient number, since it is larger than the sum of its proper divisors (165309).

20977987 is a wasteful number, since it uses less digits than its factorization.

20977987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 165308.

The product of its (nonzero) digits is 444528, while the sum is 49.

The square root of 20977987 is about 4580.1732499983. The cubic root of 20977987 is about 275.7959836209.

The spelling of 20977987 in words is "twenty million, nine hundred seventy-seven thousand, nine hundred eighty-seven".