51981985440 has 1152 divisors, whose sum is σ = 237491896320. Its totient is φ = 10305792000.

The previous prime is 51981985439. The next prime is 51981985457. The reversal of 51981985440 is 4458918915.

51981985440 is a `hidden beast` number, since 5 + 1 + 9 + 8 + 1 + 98 + 544 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 732140605 + ... + 732140675.

It is an arithmetic number, because the mean of its divisors is an integer number (206156160).

Almost surely, 2^51981985440 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 51981985440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118745948160).

51981985440 is an abundant number, since it is smaller than the sum of its proper divisors (185509910880).

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

51981985440 is a wasteful number, since it uses less digits than its factorization.

51981985440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 2073600, while the sum is 54.

The spelling of 51981985440 in words is "fifty-one billion, nine hundred eighty-one million, nine hundred eighty-five thousand, four hundred forty".