20891545920 has 504 divisors, whose sum is σ = 86701908384. Its totient is φ = 4774339584.

The previous prime is 20891545891. The next prime is 20891545933. The reversal of 20891545920 is 2954519802.

It is a happy number.

20891545920 is a `hidden beast` number, since 2 + 0 + 8 + 9 + 1 + 54 + 592 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (504).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 3807499 + ... + 3812981.

It is an arithmetic number, because the mean of its divisors is an integer number (172027596).

Almost surely, 2^20891545920 is an apocalyptic number.

20891545920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20891545920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43350954192).

20891545920 is an abundant number, since it is smaller than the sum of its proper divisors (65810362464).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20891545920 is an equidigital number, since it uses as much as digits as its factorization.

20891545920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5529 (or 5500 counting only the distinct ones).

The product of its (nonzero) digits is 259200, while the sum is 45.

The spelling of 20891545920 in words is "twenty billion, eight hundred ninety-one million, five hundred forty-five thousand, nine hundred twenty".