20983987 has 4 divisors (see below), whose sum is σ = 21169800. Its totient is φ = 20798176.

The previous prime is 20983969. The next prime is 20983997. The reversal of 20983987 is 78938902.

20983987 is an esthetic number in base 7, because in such base its adjacent digits differ by 1.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20983987 is a prime.

It is a super-3 number, since 3×20983987³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20983927) 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, 92737 + ... + 92962.

It is an arithmetic number, because the mean of its divisors is an integer number (5292450).

Almost surely, 2^20983987 is an apocalyptic number.

20983987 is a deficient number, since it is larger than the sum of its proper divisors (185813).

20983987 is a wasteful number, since it uses less digits than its factorization.

20983987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 185812.

The product of its (nonzero) digits is 217728, while the sum is 46.

The square root of 20983987 is about 4580.8282002276. The cubic root of 20983987 is about 275.8222749608.

The spelling of 20983987 in words is "twenty million, nine hundred eighty-three thousand, nine hundred eighty-seven".