51720240 has 240 divisors, whose sum is σ = 191175264. Its totient is φ = 11489280.

The previous prime is 51720199. The next prime is 51720247. The reversal of 51720240 is 4202715.

It is a tau number, because it is divible by the number of its divisors (240).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51720247) 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, 377452 + ... + 377588.

Almost surely, 2^51720240 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 51720240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95587632).

51720240 is an abundant number, since it is smaller than the sum of its proper divisors (139455024).

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

51720240 is a wasteful number, since it uses less digits than its factorization.

51720240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 188 (or 171 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 21.

The square root of 51720240 is about 7191.6785245171. The cubic root of 51720240 is about 372.5805480213.

Adding to 51720240 its reverse (4202715), we get a palindrome (55922955).

The spelling of 51720240 in words is "fifty-one million, seven hundred twenty thousand, two hundred forty".