51664991 has 4 divisors (see below), whose sum is σ = 59045712. Its totient is φ = 44284272.

The previous prime is 51664981. The next prime is 51664993. The reversal of 51664991 is 19946615.

51664991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 51664991 - 2¹⁰ = 51663967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51664993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3690350 + ... + 3690363.

It is an arithmetic number, because the mean of its divisors is an integer number (14761428).

Almost surely, 2^51664991 is an apocalyptic number.

51664991 is a deficient number, since it is larger than the sum of its proper divisors (7380721).

51664991 is an equidigital number, since it uses as much as digits as its factorization.

51664991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7380720.

The product of its digits is 58320, while the sum is 41.

The square root of 51664991 is about 7187.8363225661. The cubic root of 51664991 is about 372.4478337830.

The spelling of 51664991 in words is "fifty-one million, six hundred sixty-four thousand, nine hundred ninety-one".