20913987 has 8 divisors (see below), whose sum is σ = 27985680. Its totient is φ = 13892480.

The previous prime is 20913967. The next prime is 20914001. The reversal of 20913987 is 78931902.

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

It is a cyclic number.

It is not a de Polignac number, because 20913987 - 2¹⁸ = 20651843 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20913967) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11562 + ... + 13247.

It is an arithmetic number, because the mean of its divisors is an integer number (3498210).

Almost surely, 2^20913987 is an apocalyptic number.

20913987 is a deficient number, since it is larger than the sum of its proper divisors (7071693).

20913987 is a wasteful number, since it uses less digits than its factorization.

20913987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25093.

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 20913987 is about 4573.1812778415. The cubic root of 20913987 is about 275.5152302234.

It can be divided in two parts, 209 and 13987, that added together give a triangular number (14196 = T₁₆₈).

The spelling of 20913987 in words is "twenty million, nine hundred thirteen thousand, nine hundred eighty-seven".