51381820 has 48 divisors (see below), whose sum is σ = 130576320. Its totient is φ = 16579584.

The previous prime is 51381817. The next prime is 51381829. The reversal of 51381820 is 2818315.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51381829) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8415 + ... + 13174.

It is an arithmetic number, because the mean of its divisors is an integer number (2720340).

Almost surely, 2^51381820 is an apocalyptic number.

It is an amenable number.

51381820 is an abundant number, since it is smaller than the sum of its proper divisors (79194500).

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

51381820 is a wasteful number, since it uses less digits than its factorization.

51381820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21622 (or 21620 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 51381820 is about 7168.1113272605. Note that the first 3 decimals coincide. The cubic root of 51381820 is about 371.7661362012.

The spelling of 51381820 in words is "fifty-one million, three hundred eighty-one thousand, eight hundred twenty".