660551621 has 2 divisors, whose sum is σ = 660551622. Its totient is φ = 660551620.

The previous prime is 660551611. The next prime is 660551653. The reversal of 660551621 is 126155066.

It is an a-pointer prime, because the next prime (660551653) can be obtained adding 660551621 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 372876100 + 287675521 = 19310^2 + 16961^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-660551621 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (660551611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330275810 + 330275811.

It is an arithmetic number, because the mean of its divisors is an integer number (330275811).

Almost surely, 2^660551621 is an apocalyptic number.

It is an amenable number.

660551621 is a deficient number, since it is larger than the sum of its proper divisors (1).

660551621 is an equidigital number, since it uses as much as digits as its factorization.

660551621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10800, while the sum is 32.

The square root of 660551621 is about 25701.1988241794. The cubic root of 660551621 is about 870.9012640267.

It can be divided in two parts, 66055 and 1621, that added together give a palindrome (67676).

The spelling of 660551621 in words is "six hundred sixty million, five hundred fifty-one thousand, six hundred twenty-one".