4991209621 has 2 divisors, whose sum is σ = 4991209622. Its totient is φ = 4991209620.

The previous prime is 4991209583. The next prime is 4991209627. The reversal of 4991209621 is 1269021994.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2620006596 + 2371203025 = 51186^2 + 48695^2 .

It is a cyclic number.

It is not a de Polignac number, because 4991209621 - 2⁹ = 4991209109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (4991209627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2495604810 + 2495604811.

It is an arithmetic number, because the mean of its divisors is an integer number (2495604811).

Almost surely, 2^4991209621 is an apocalyptic number.

It is an amenable number.

4991209621 is a deficient number, since it is larger than the sum of its proper divisors (1).

4991209621 is an equidigital number, since it uses as much as digits as its factorization.

4991209621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 69984, while the sum is 43.

The square root of 4991209621 is about 70648.4934092724. The cubic root of 4991209621 is about 1708.9732697428.

The spelling of 4991209621 in words is "four billion, nine hundred ninety-one million, two hundred nine thousand, six hundred twenty-one".