821261784817540 has 192 divisors, whose sum is σ = 1948837846072320. Its totient is φ = 287968911552000.

The previous prime is 821261784817493. The next prime is 821261784817543. The reversal of 821261784817540 is 45718487162128.

It is a super-3 number, since 3×821261784817540³ (a number of 46 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (821261784817543) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 16461095995 + ... + 16461145885.

It is an arithmetic number, because the mean of its divisors is an integer number (10150197114960).

Almost surely, 2^{821261784817540} 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 821261784817540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (974418923036160).

821261784817540 is an abundant number, since it is smaller than the sum of its proper divisors (1127576061254780).

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

821261784817540 is a wasteful number, since it uses less digits than its factorization.

821261784817540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53234 (or 53232 counting only the distinct ones).

The product of its (nonzero) digits is 48168960, while the sum is 64.

The spelling of 821261784817540 in words is "eight hundred twenty-one trillion, two hundred sixty-one billion, seven hundred eighty-four million, eight hundred seventeen thousand, five hundred forty".