21851735256540 has 360 divisors, whose sum is σ = 79648029036576. Its totient is φ = 4912792819200.

The previous prime is 21851735256509. The next prime is 21851735256599. The reversal of 21851735256540 is 4565253715812.

21851735256540 is a `hidden beast` number, since 2 + 1 + 8 + 5 + 1 + 7 + 35 + 2 + 565 + 40 = 666.

It is a super-2 number, since 2×21851735256540² (a number of 27 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 41937210 + ... + 42455070.

Almost surely, 2^{21851735256540} is an apocalyptic number.

21851735256540 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 21851735256540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39824014518288).

21851735256540 is an abundant number, since it is smaller than the sum of its proper divisors (57796293780036).

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

21851735256540 is a wasteful number, since it uses less digits than its factorization.

21851735256540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 518011 (or 517939 counting only the distinct ones).

The product of its (nonzero) digits is 10080000, while the sum is 54.

The spelling of 21851735256540 in words is "twenty-one trillion, eight hundred fifty-one billion, seven hundred thirty-five million, two hundred fifty-six thousand, five hundred forty".