85105721 has 2 divisors, whose sum is σ = 85105722. Its totient is φ = 85105720.

The previous prime is 85105711. The next prime is 85105777. The reversal of 85105721 is 12750158.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81631225 + 3474496 = 9035^2 + 1864^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-85105721 is a prime.

It is not a weakly prime, because it can be changed into another prime (85105711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42552860 + 42552861.

It is an arithmetic number, because the mean of its divisors is an integer number (42552861).

Almost surely, 2^85105721 is an apocalyptic number.

It is an amenable number.

85105721 is a deficient number, since it is larger than the sum of its proper divisors (1).

85105721 is an equidigital number, since it uses as much as digits as its factorization.

85105721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2800, while the sum is 29.

The square root of 85105721 is about 9225.2762018272. The cubic root of 85105721 is about 439.8651808021.

Adding to 85105721 its reverse (12750158), we get a palindrome (97855879).

The spelling of 85105721 in words is "eighty-five million, one hundred five thousand, seven hundred twenty-one".