51861780 has 72 divisors (see below), whose sum is σ = 164166912. Its totient is φ = 13227456.

The previous prime is 51861779. The next prime is 51861793. The reversal of 51861780 is 8716815.

51861780 is a `hidden beast` number, since 518 + 61 + 7 + 80 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2124 + ... + 10403.

It is an arithmetic number, because the mean of its divisors is an integer number (2280096).

Almost surely, 2^51861780 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 51861780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (82083456).

51861780 is an abundant number, since it is smaller than the sum of its proper divisors (112305132).

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

51861780 is a wasteful number, since it uses less digits than its factorization.

51861780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12565 (or 12560 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 36.

The square root of 51861780 is about 7201.5123411683. The cubic root of 51861780 is about 372.9201121716.

The spelling of 51861780 in words is "fifty-one million, eight hundred sixty-one thousand, seven hundred eighty".