900821 has 2 divisors, whose sum is σ = 900822. Its totient is φ = 900820.

The previous prime is 900817. The next prime is 900863. The reversal of 900821 is 128009.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 819025 + 81796 = 905^2 + 286^2 .

It is a cyclic number.

It is not a de Polignac number, because 900821 - 2² = 900817 is a prime.

It is a super-2 number, since 2×900821² = 1622956948082, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 900793 and 900802.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (900121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 450410 + 450411.

It is an arithmetic number, because the mean of its divisors is an integer number (450411).

2⁹⁰⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

900821 is a deficient number, since it is larger than the sum of its proper divisors (1).

900821 is an equidigital number, since it uses as much as digits as its factorization.

900821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 900821 is about 949.1159044079. The cubic root of 900821 is about 96.5782875671.

The spelling of 900821 in words is "nine hundred thousand, eight hundred twenty-one".