821540807540 has 24 divisors (see below), whose sum is σ = 1725272956680. Its totient is φ = 328609225728.

The previous prime is 821540807539. The next prime is 821540807543. The reversal of 821540807540 is 45708045128.

It can be written as a sum of positive squares in 4 ways, for example, as 37724515984 + 783816291556 = 194228^2 + 885334^2 .

It is a junction number, because it is equal to n+sod(n) for n = 821540807491 and 821540807500.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821540807543) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 561104 + ... + 1399256.

It is an arithmetic number, because the mean of its divisors is an integer number (71886373195).

Almost surely, 2^821540807540 is an apocalyptic number.

It is an amenable number.

821540807540 is an abundant number, since it is smaller than the sum of its proper divisors (903732149140).

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

821540807540 is a wasteful number, since it uses less digits than its factorization.

821540807540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 887171 (or 887169 counting only the distinct ones).

The product of its (nonzero) digits is 358400, while the sum is 44.

The spelling of 821540807540 in words is "eight hundred twenty-one billion, five hundred forty million, eight hundred seven thousand, five hundred forty".