821384261 has 4 divisors (see below), whose sum is σ = 825640332. Its totient is φ = 817128192.

The previous prime is 821384243. The next prime is 821384287. The reversal of 821384261 is 162483128.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 409050625 + 412333636 = 20225^2 + 20306^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-821384261 is a prime.

It is a super-2 number, since 2×821384261² = 1349344208437032242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821384561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2127746 + ... + 2128131.

It is an arithmetic number, because the mean of its divisors is an integer number (206410083).

Almost surely, 2^821384261 is an apocalyptic number.

It is an amenable number.

821384261 is a deficient number, since it is larger than the sum of its proper divisors (4256071).

821384261 is a wasteful number, since it uses less digits than its factorization.

821384261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4256070.

The product of its digits is 18432, while the sum is 35.

The square root of 821384261 is about 28659.8021800570. The cubic root of 821384261 is about 936.5165551134.

The spelling of 821384261 in words is "eight hundred twenty-one million, three hundred eighty-four thousand, two hundred sixty-one".