721047661 has 2 divisors, whose sum is σ = 721047662. Its totient is φ = 721047660.

The previous prime is 721047653. The next prime is 721047667. The reversal of 721047661 is 166740127.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 641659561 + 79388100 = 25331^2 + 8910^2 .

It is an emirp because it is prime and its reverse (166740127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 721047661 - 2³ = 721047653 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721047667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360523830 + 360523831.

It is an arithmetic number, because the mean of its divisors is an integer number (360523831).

Almost surely, 2^721047661 is an apocalyptic number.

It is an amenable number.

721047661 is a deficient number, since it is larger than the sum of its proper divisors (1).

721047661 is an equidigital number, since it uses as much as digits as its factorization.

721047661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 14112, while the sum is 34.

The square root of 721047661 is about 26852.3306437263. The cubic root of 721047661 is about 896.7154602015.

Adding to 721047661 its reverse (166740127), we get a palindrome (887787788).

The spelling of 721047661 in words is "seven hundred twenty-one million, forty-seven thousand, six hundred sixty-one".