20420981280 has 648 divisors, whose sum is σ = 84389606028. Its totient is φ = 4655895552.

The previous prime is 20420981279. The next prime is 20420981297. The reversal of 20420981280 is 8218902402.

20420981280 is a `hidden beast` number, since 20 + 420 + 98 + 128 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 20415837456 + 5143824 = 142884^2 + 2268^2 .

It is a tau number, because it is divible by the number of its divisors (648).

It is a super-2 number, since 2×20420981280² (a number of 21 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 107 ways as a sum of consecutive naturals, for example, 51438042 + ... + 51438438.

Almost surely, 2^20420981280 is an apocalyptic number.

20420981280 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 20420981280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42194803014).

20420981280 is an abundant number, since it is smaller than the sum of its proper divisors (63968624748).

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

20420981280 is an frugal number, since it uses more digits than its factorization.

20420981280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 450 (or 414 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The spelling of 20420981280 in words is "twenty billion, four hundred twenty million, nine hundred eighty-one thousand, two hundred eighty".