821642 has 8 divisors (see below), whose sum is σ = 1244100. Its totient is φ = 406944.

The previous prime is 821641. The next prime is 821647. The reversal of 821642 is 246128.

It can be written as a sum of positive squares in 2 ways, for example, as 758641 + 63001 = 871^2 + 251^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (821641) 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, 1667 + ... + 2102.

2⁸²¹⁶⁴² is an apocalyptic number.

821642 is a deficient number, since it is larger than the sum of its proper divisors (422458).

821642 is a wasteful number, since it uses less digits than its factorization.

821642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3880.

The product of its digits is 768, while the sum is 23.

The square root of 821642 is about 906.4447032224. Note that the first 3 decimals coincide. The cubic root of 821642 is about 93.6614500176.

The spelling of 821642 in words is "eight hundred twenty-one thousand, six hundred forty-two".