21489813891 has 128 divisors (see below), whose sum is σ = 40175206400. Its totient is φ = 11051873280.

The previous prime is 21489813889. The next prime is 21489813899. The reversal of 21489813891 is 19831898412.

It is a happy number.

21489813891 is a `hidden beast` number, since 2 + 1 + 489 + 81 + 3 + 89 + 1 = 666.

It is not a de Polignac number, because 21489813891 - 2¹ = 21489813889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21489813899) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 19033815 + ... + 19034943.

It is an arithmetic number, because the mean of its divisors is an integer number (313868800).

Almost surely, 2^21489813891 is an apocalyptic number.

21489813891 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21489813891 is a deficient number, since it is larger than the sum of its proper divisors (18685392509).

21489813891 is a wasteful number, since it uses less digits than its factorization.

21489813891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1346 (or 1340 counting only the distinct ones).

The product of its digits is 995328, while the sum is 54.

The spelling of 21489813891 in words is "twenty-one billion, four hundred eighty-nine million, eight hundred thirteen thousand, eight hundred ninety-one".