21091243761408 has 144 divisors (see below), whose sum is σ = 57514561251840. Its totient is φ = 6858414563328.

The previous prime is 21091243761391. The next prime is 21091243761437. The reversal of 21091243761408 is 80416734219012.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a congruent number.

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, 10129828 + ... + 12033116.

It is an arithmetic number, because the mean of its divisors is an integer number (399406675360).

Almost surely, 2^{21091243761408} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21091243761408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28757280625920).

21091243761408 is an abundant number, since it is smaller than the sum of its proper divisors (36423317490432).

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

21091243761408 is a wasteful number, since it uses less digits than its factorization.

21091243761408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1903662 (or 1903648 counting only the distinct ones).

The product of its (nonzero) digits is 580608, while the sum is 48.

The spelling of 21091243761408 in words is "twenty-one trillion, ninety-one billion, two hundred forty-three million, seven hundred sixty-one thousand, four hundred eight".