51440220 has 216 divisors, whose sum is σ = 179852400. Its totient is φ = 11860992.

The previous prime is 51440203. The next prime is 51440237. The reversal of 51440220 is 2204415.

51440220 is a `hidden beast` number, since 5 + 1 + 440 + 220 = 666.

It is an interprime number because it is at equal distance from previous prime (51440203) and next prime (51440237).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 51440193 and 51440202.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 577936 + ... + 578024.

It is an arithmetic number, because the mean of its divisors is an integer number (832650).

Almost surely, 2^51440220 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 51440220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (89926200).

51440220 is an abundant number, since it is smaller than the sum of its proper divisors (128412180).

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

51440220 is a wasteful number, since it uses less digits than its factorization.

51440220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 149 (or 131 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 51440220 is about 7172.1837678632. The cubic root of 51440220 is about 371.9069312788.

Adding to 51440220 its reverse (2204415), we get a palindrome (53644635).

The spelling of 51440220 in words is "fifty-one million, four hundred forty thousand, two hundred twenty".