65647721 has 2 divisors, whose sum is σ = 65647722. Its totient is φ = 65647720.

The previous prime is 65647709. The next prime is 65647723. The reversal of 65647721 is 12774656.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62173225 + 3474496 = 7885^2 + 1864^2 .

It is a cyclic number.

It is not a de Polignac number, because 65647721 - 2¹⁸ = 65385577 is a prime.

Together with 65647723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (65647723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32823860 + 32823861.

It is an arithmetic number, because the mean of its divisors is an integer number (32823861).

Almost surely, 2^65647721 is an apocalyptic number.

It is an amenable number.

65647721 is a deficient number, since it is larger than the sum of its proper divisors (1).

65647721 is an equidigital number, since it uses as much as digits as its factorization.

65647721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 70560, while the sum is 38.

The square root of 65647721 is about 8102.3281222128. The cubic root of 65647721 is about 403.4037068806.

The spelling of 65647721 in words is "sixty-five million, six hundred forty-seven thousand, seven hundred twenty-one".