51251320440 has 192 divisors, whose sum is σ = 173967393600. Its totient is φ = 13060878336.

The previous prime is 51251320433. The next prime is 51251320447. The reversal of 51251320440 is 4402315215.

51251320440 is a `hidden beast` number, since 51 + 251 + 320 + 4 + 40 = 666.

It is an interprime number because it is at equal distance from previous prime (51251320433) and next prime (51251320447).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51251320447) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 12326842 + ... + 12330998.

It is an arithmetic number, because the mean of its divisors is an integer number (906080175).

Almost surely, 2^51251320440 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 51251320440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (86983696800).

51251320440 is an abundant number, since it is smaller than the sum of its proper divisors (122716073160).

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

51251320440 is a wasteful number, since it uses less digits than its factorization.

51251320440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5686 (or 5679 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 27.

Adding to 51251320440 its reverse (4402315215), we get a palindrome (55653635655).

The spelling of 51251320440 in words is "fifty-one billion, two hundred fifty-one million, three hundred twenty thousand, four hundred forty".