51209191 has 4 divisors (see below), whose sum is σ = 55864584. Its totient is φ = 46553800.

The previous prime is 51209111. The next prime is 51209233. The reversal of 51209191 is 19190215.

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 51209191 - 2²⁵ = 17654759 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 (51209101) 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, 2327680 + ... + 2327701.

It is an arithmetic number, because the mean of its divisors is an integer number (13966146).

Almost surely, 2^51209191 is an apocalyptic number.

51209191 is a deficient number, since it is larger than the sum of its proper divisors (4655393).

51209191 is a wasteful number, since it uses less digits than its factorization.

51209191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4655392.

The product of its (nonzero) digits is 810, while the sum is 28.

The square root of 51209191 is about 7156.0597398289. The cubic root of 51209191 is about 371.3493245487.

The spelling of 51209191 in words is "fifty-one million, two hundred nine thousand, one hundred ninety-one".