51993209 has 4 divisors (see below), whose sum is σ = 52010100. Its totient is φ = 51976320.

The previous prime is 51993203. The next prime is 51993211. The reversal of 51993209 is 90239915.

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 18318400 + 33674809 = 4280^2 + 5803^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51993209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51993203) 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, 2372 + ... + 10469.

It is an arithmetic number, because the mean of its divisors is an integer number (13002525).

Almost surely, 2^51993209 is an apocalyptic number.

It is an amenable number.

51993209 is a deficient number, since it is larger than the sum of its proper divisors (16891).

51993209 is a wasteful number, since it uses less digits than its factorization.

51993209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16890.

The product of its (nonzero) digits is 21870, while the sum is 38.

The square root of 51993209 is about 7210.6316644244. The cubic root of 51993209 is about 373.2348665876.

The spelling of 51993209 in words is "fifty-one million, nine hundred ninety-three thousand, two hundred nine".