821721712 has 80 divisors (see below), whose sum is σ = 1886736384. Its totient is φ = 339264000.

The previous prime is 821721697. The next prime is 821721731. The reversal of 821721712 is 217127128.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1079412 + ... + 1080172.

Almost surely, 2^821721712 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 821721712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (943368192).

821721712 is an abundant number, since it is smaller than the sum of its proper divisors (1065014672).

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

821721712 is a wasteful number, since it uses less digits than its factorization.

821721712 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1118 (or 1112 counting only the distinct ones).

The product of its digits is 3136, while the sum is 31.

The square root of 821721712 is about 28665.6887585141. The cubic root of 821721712 is about 936.6447879007.

It can be divided in two parts, 8217 and 21712, that added together give a square (29929 = 173²).

The spelling of 821721712 in words is "eight hundred twenty-one million, seven hundred twenty-one thousand, seven hundred twelve".