51215220 has 192 divisors, whose sum is σ = 193052160. Its totient is φ = 11003904.

The previous prime is 51215209. The next prime is 51215231. The reversal of 51215220 is 2251215.

51215220 is a `hidden beast` number, since 512 + 152 + 2 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (51215209) and next prime (51215231).

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 = 51215193 and 51215202.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 63862 + ... + 64658.

It is an arithmetic number, because the mean of its divisors is an integer number (1005480).

Almost surely, 2^51215220 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 51215220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (96526080).

51215220 is an abundant number, since it is smaller than the sum of its proper divisors (141836940).

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

51215220 is a wasteful number, since it uses less digits than its factorization.

51215220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 839 (or 831 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 51215220 is about 7156.4809788052. The cubic root of 51215220 is about 371.3638973052.

Adding to 51215220 its reverse (2251215), we get a palindrome (53466435).

The spelling of 51215220 in words is "fifty-one million, two hundred fifteen thousand, two hundred twenty".