51961991 has 4 divisors (see below), whose sum is σ = 54221232. Its totient is φ = 49702752.

The previous prime is 51961967. The next prime is 51961999. The reversal of 51961991 is 19916915.

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 51961991 - 2⁶ = 51961927 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 (51961999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1129586 + ... + 1129631.

It is an arithmetic number, because the mean of its divisors is an integer number (13555308).

Almost surely, 2^51961991 is an apocalyptic number.

51961991 is a deficient number, since it is larger than the sum of its proper divisors (2259241).

51961991 is a wasteful number, since it uses less digits than its factorization.

51961991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2259240.

The product of its digits is 21870, while the sum is 41.

The square root of 51961991 is about 7208.4666191916. The cubic root of 51961991 is about 373.1601518377.

The spelling of 51961991 in words is "fifty-one million, nine hundred sixty-one thousand, nine hundred ninety-one".