821655405090 has 160 divisors (see below), whose sum is σ = 2385294634800. Its totient is φ = 201743156736.

The previous prime is 821655405083. The next prime is 821655405101. The reversal of 821655405090 is 90504556128.

821655405090 is a `hidden beast` number, since 8 + 2 + 1 + 6 + 554 + 0 + 5 + 0 + 90 = 666.

821655405090 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 8 ways, for example, as 166123901889 + 655531503201 = 407583^2 + 809649^2 .

It is a super-2 number, since 2×821655405090² (a number of 25 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 4082136 + ... + 4278684.

Almost surely, 2^821655405090 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 821655405090, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1192647317400).

821655405090 is an abundant number, since it is smaller than the sum of its proper divisors (1563639229710).

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

821655405090 is a wasteful number, since it uses less digits than its factorization.

821655405090 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 196978 (or 196969 counting only the distinct ones).

The product of its (nonzero) digits is 432000, while the sum is 45.

The spelling of 821655405090 in words is "eight hundred twenty-one billion, six hundred fifty-five million, four hundred five thousand, ninety".