820821031 has 2 divisors, whose sum is σ = 820821032. Its totient is φ = 820821030.

The previous prime is 820821011. The next prime is 820821037. The reversal of 820821031 is 130128028.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 820821031 - 2⁵ = 820820999 is a prime.

It is a super-2 number, since 2×820821031² = 1347494329863805922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 820820987 and 820821005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (820821037) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410410515 + 410410516.

It is an arithmetic number, because the mean of its divisors is an integer number (410410516).

Almost surely, 2^820821031 is an apocalyptic number.

820821031 is a deficient number, since it is larger than the sum of its proper divisors (1).

820821031 is an equidigital number, since it uses as much as digits as its factorization.

820821031 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 820821031 is about 28649.9743629903. The cubic root of 820821031 is about 936.3024471111.

Adding to 820821031 its reverse (130128028), we get a palindrome (950949059).

The spelling of 820821031 in words is "eight hundred twenty million, eight hundred twenty-one thousand, thirty-one".