20861511997648 has 80 divisors (see below), whose sum is σ = 46401876518400. Its totient is φ = 8900304657408.

The previous prime is 20861511997631. The next prime is 20861511997657. The reversal of 20861511997648 is 84679911516802.

It is a super-2 number, since 2×20861511997648² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 120920953 + ... + 121093351.

It is an arithmetic number, because the mean of its divisors is an integer number (580023456480).

Almost surely, 2^{20861511997648} is an apocalyptic number.

20861511997648 is a gapful number since it is divisible by the number (28) 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 20861511997648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23200938259200).

20861511997648 is an abundant number, since it is smaller than the sum of its proper divisors (25540364520752).

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

20861511997648 is a wasteful number, since it uses less digits than its factorization.

20861511997648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177284 (or 177278 counting only the distinct ones).

The product of its (nonzero) digits is 52254720, while the sum is 67.

The spelling of 20861511997648 in words is "twenty trillion, eight hundred sixty-one billion, five hundred eleven million, nine hundred ninety-seven thousand, six hundred forty-eight".