51091919640 has 640 divisors, whose sum is σ = 184666521600. Its totient is φ = 12648130560.

The previous prime is 51091919623. The next prime is 51091919689. The reversal of 51091919640 is 4691919015.

51091919640 is a `hidden beast` number, since 510 + 9 + 1 + 9 + 1 + 96 + 40 = 666.

It is a super-2 number, since 2×51091919640² (a number of 22 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 372933652 + ... + 372933788.

It is an arithmetic number, because the mean of its divisors is an integer number (288541440).

Almost surely, 2^51091919640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 51091919640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (92333260800).

51091919640 is an abundant number, since it is smaller than the sum of its proper divisors (133574601960).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

51091919640 is a wasteful number, since it uses less digits than its factorization.

51091919640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 317 (or 304 counting only the distinct ones).

The product of its (nonzero) digits is 87480, while the sum is 45.

The spelling of 51091919640 in words is "fifty-one billion, ninety-one million, nine hundred nineteen thousand, six hundred forty".