20421240155440 has 80 divisors (see below), whose sum is σ = 47830868271360. Its totient is φ = 8108037816320.

The previous prime is 20421240155413. The next prime is 20421240155497. The reversal of 20421240155440 is 4455104212402.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 20421240155396 and 20421240155405.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 112479456 + ... + 112660864.

It is an arithmetic number, because the mean of its divisors is an integer number (597885853392).

Almost surely, 2^{20421240155440} is an apocalyptic number.

20421240155440 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 20421240155440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23915434135680).

20421240155440 is an abundant number, since it is smaller than the sum of its proper divisors (27409628115920).

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

20421240155440 is a wasteful number, since it uses less digits than its factorization.

20421240155440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 191830 (or 191824 counting only the distinct ones).

The product of its (nonzero) digits is 51200, while the sum is 34.

Adding to 20421240155440 its reverse (4455104212402), we get a palindrome (24876344367842).

The spelling of 20421240155440 in words is "twenty trillion, four hundred twenty-one billion, two hundred forty million, one hundred fifty-five thousand, four hundred forty".