551611721 has 2 divisors, whose sum is σ = 551611722. Its totient is φ = 551611720.

The previous prime is 551611717. The next prime is 551611727. The reversal of 551611721 is 127116155.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 483780025 + 67831696 = 21995^2 + 8236^2 .

It is a cyclic number.

It is not a de Polignac number, because 551611721 - 2² = 551611717 is a prime.

It is not a weakly prime, because it can be changed into another prime (551611727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 275805860 + 275805861.

It is an arithmetic number, because the mean of its divisors is an integer number (275805861).

Almost surely, 2^551611721 is an apocalyptic number.

It is an amenable number.

551611721 is a deficient number, since it is larger than the sum of its proper divisors (1).

551611721 is an equidigital number, since it uses as much as digits as its factorization.

551611721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2100, while the sum is 29.

The square root of 551611721 is about 23486.4156694886. The cubic root of 551611721 is about 820.1208036378.

Adding to 551611721 its reverse (127116155), we get a palindrome (678727876).

The spelling of 551611721 in words is "five hundred fifty-one million, six hundred eleven thousand, seven hundred twenty-one".