821906 has 4 divisors (see below), whose sum is σ = 1232862. Its totient is φ = 410952.

The previous prime is 821897. The next prime is 821911. The reversal of 821906 is 609128.

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

It can be written as a sum of positive squares in only one way, i.e., 502681 + 319225 = 709^2 + 565^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 205475 + ... + 205478.

2⁸²¹⁹⁰⁶ is an apocalyptic number.

821906 is a deficient number, since it is larger than the sum of its proper divisors (410956).

821906 is a wasteful number, since it uses less digits than its factorization.

821906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 410955.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 821906 is about 906.5903154126. The cubic root of 821906 is about 93.6714803288.

The spelling of 821906 in words is "eight hundred twenty-one thousand, nine hundred six".