51399809 has 4 divisors (see below), whose sum is σ = 51908820. Its totient is φ = 50890800.

The previous prime is 51399793. The next prime is 51399827. The reversal of 51399809 is 90899315.

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

It can be written as a sum of positive squares in 2 ways, for example, as 32171584 + 19228225 = 5672^2 + 4385^2 .

It is a cyclic number.

It is not a de Polignac number, because 51399809 - 2⁴ = 51399793 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 51399809.

It is not an unprimeable number, because it can be changed into a prime (51399839) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 254354 + ... + 254555.

It is an arithmetic number, because the mean of its divisors is an integer number (12977205).

Almost surely, 2^51399809 is an apocalyptic number.

It is an amenable number.

51399809 is a deficient number, since it is larger than the sum of its proper divisors (509011).

51399809 is a wasteful number, since it uses less digits than its factorization.

51399809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 509010.

The product of its (nonzero) digits is 87480, while the sum is 44.

The square root of 51399809 is about 7169.3660110222. The cubic root of 51399809 is about 371.8095167893.

The spelling of 51399809 in words is "fifty-one million, three hundred ninety-nine thousand, eight hundred nine".