20405920640 has 128 divisors (see below), whose sum is σ = 56890296000. Its totient is φ = 6996240384.

The previous prime is 20405920631. The next prime is 20405920657. The reversal of 20405920640 is 4602950402.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 20405920597 and 20405920606.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 173042 + ... + 265998.

Almost surely, 2^20405920640 is an apocalyptic number.

20405920640 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 20405920640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28445148000).

20405920640 is an abundant number, since it is smaller than the sum of its proper divisors (36484375360).

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

20405920640 is an frugal number, since it uses more digits than its factorization.

20405920640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92997 (or 92971 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 32.

The spelling of 20405920640 in words is "twenty billion, four hundred five million, nine hundred twenty thousand, six hundred forty".