20987139 has 8 divisors (see below), whose sum is σ = 28633792. Its totient is φ = 13665960.

The previous prime is 20987119. The next prime is 20987143. The reversal of 20987139 is 93178902.

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

It is not a de Polignac number, because 20987139 - 2⁸ = 20986883 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20987097 and 20987106.

It is not an unprimeable number, because it can be changed into a prime (20987119) 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, 81217 + ... + 81474.

It is an arithmetic number, because the mean of its divisors is an integer number (3579224).

Almost surely, 2^20987139 is an apocalyptic number.

20987139 is a deficient number, since it is larger than the sum of its proper divisors (7646653).

20987139 is a wasteful number, since it uses less digits than its factorization.

20987139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 162737.

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

The square root of 20987139 is about 4581.1722298992. The cubic root of 20987139 is about 275.8360846702.

The spelling of 20987139 in words is "twenty million, nine hundred eighty-seven thousand, one hundred thirty-nine".