51991669 has 4 divisors (see below), whose sum is σ = 52506540. Its totient is φ = 51476800.

The previous prime is 51991663. The next prime is 51991711. The reversal of 51991669 is 96619915.

51991669 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 can be written as a sum of positive squares in 2 ways, for example, as 49702500 + 2289169 = 7050^2 + 1513^2 .

It is a cyclic number.

It is not a de Polignac number, because 51991669 - 2²³ = 43603061 is a prime.

It is a super-2 number, since 2×51991669² = 5406267290811122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51991663) 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, 257284 + ... + 257485.

It is an arithmetic number, because the mean of its divisors is an integer number (13126635).

Almost surely, 2^51991669 is an apocalyptic number.

It is an amenable number.

51991669 is a deficient number, since it is larger than the sum of its proper divisors (514871).

51991669 is a wasteful number, since it uses less digits than its factorization.

51991669 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 514870.

The product of its digits is 131220, while the sum is 46.

The square root of 51991669 is about 7210.5248768727. The cubic root of 51991669 is about 373.2311815720.

The spelling of 51991669 in words is "fifty-one million, nine hundred ninety-one thousand, six hundred sixty-nine".