820138121 has 12 divisors (see below), whose sum is σ = 904719732. Its totient is φ = 742896000.

The previous prime is 820138091. The next prime is 820138177. The reversal of 820138121 is 121831028.

It can be written as a sum of positive squares in 2 ways, for example, as 392475721 + 427662400 = 19811^2 + 20680^2 .

It is not a de Polignac number, because 820138121 - 2⁶ = 820138057 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (820138181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 21941 + ... + 46061.

It is an arithmetic number, because the mean of its divisors is an integer number (75393311).

Almost surely, 2^820138121 is an apocalyptic number.

It is an amenable number.

820138121 is a deficient number, since it is larger than the sum of its proper divisors (84581611).

820138121 is a wasteful number, since it uses less digits than its factorization.

820138121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24424 (or 24413 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 820138121 is about 28638.0537222766. The cubic root of 820138121 is about 936.0427121675.

Adding to 820138121 its reverse (121831028), we get a palindrome (941969149).

The spelling of 820138121 in words is "eight hundred twenty million, one hundred thirty-eight thousand, one hundred twenty-one".