20988891 has 48 divisors (see below), whose sum is σ = 39057408. Its totient is φ = 10540800.

The previous prime is 20988881. The next prime is 20988893. The reversal of 20988891 is 19888902.

It is not a de Polignac number, because 20988891 - 2⁶ = 20988827 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20988893) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 20995 + ... + 21971.

It is an arithmetic number, because the mean of its divisors is an integer number (813696).

Almost surely, 2^20988891 is an apocalyptic number.

20988891 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

20988891 is a deficient number, since it is larger than the sum of its proper divisors (18068517).

20988891 is a wasteful number, since it uses less digits than its factorization.

20988891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1032 (or 1029 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 45.

The square root of 20988891 is about 4581.3634433430. The cubic root of 20988891 is about 275.8437600275.

The spelling of 20988891 in words is "twenty million, nine hundred eighty-eight thousand, eight hundred ninety-one".