51231220 has 48 divisors (see below), whose sum is σ = 116928000. Its totient is φ = 18783360.

The previous prime is 51231211. The next prime is 51231223. The reversal of 51231220 is 2213215.

It is a junction number, because it is equal to n+sod(n) for n = 51231194 and 51231203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51231223) 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, 9606 + ... + 13954.

It is an arithmetic number, because the mean of its divisors is an integer number (2436000).

Almost surely, 2^51231220 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 51231220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (58464000).

51231220 is an abundant number, since it is smaller than the sum of its proper divisors (65696780).

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

51231220 is a wasteful number, since it uses less digits than its factorization.

51231220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4408 (or 4406 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 51231220 is about 7157.5987593606. The cubic root of 51231220 is about 371.4025655221.

Adding to 51231220 its reverse (2213215), we get a palindrome (53444435).

The spelling of 51231220 in words is "fifty-one million, two hundred thirty-one thousand, two hundred twenty".