51664661 has 2 divisors, whose sum is σ = 51664662. Its totient is φ = 51664660.

The previous prime is 51664637. The next prime is 51664663. The reversal of 51664661 is 16646615.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 36602500 + 15062161 = 6050^2 + 3881^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51664661 is a prime.

Together with 51664663, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51664663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25832330 + 25832331.

It is an arithmetic number, because the mean of its divisors is an integer number (25832331).

Almost surely, 2^51664661 is an apocalyptic number.

It is an amenable number.

51664661 is a deficient number, since it is larger than the sum of its proper divisors (1).

51664661 is an equidigital number, since it uses as much as digits as its factorization.

51664661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 35.

The square root of 51664661 is about 7187.8133670818. The cubic root of 51664661 is about 372.4470408022.

It can be divided in two parts, 51664 and 661, that added together give a palindrome (52325).

The spelling of 51664661 in words is "fifty-one million, six hundred sixty-four thousand, six hundred sixty-one".