51187221 has 24 divisors (see below), whose sum is σ = 81192384. Its totient is φ = 32114880.

The previous prime is 51187219. The next prime is 51187247. The reversal of 51187221 is 12278115.

It is not a de Polignac number, because 51187221 - 2¹ = 51187219 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51187211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2065 + ... + 10326.

It is an arithmetic number, because the mean of its divisors is an integer number (3383016).

Almost surely, 2^51187221 is an apocalyptic number.

51187221 is a gapful number since it is divisible by the number (51) formed by its first and last digit.

51187221 is the 4131-st octagonal number.

It is an amenable number.

51187221 is a deficient number, since it is larger than the sum of its proper divisors (30005163).

51187221 is a wasteful number, since it uses less digits than its factorization.

51187221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12423 (or 12411 counting only the distinct ones).

The product of its digits is 1120, while the sum is 27.

The square root of 51187221 is about 7154.5245125026. The cubic root of 51187221 is about 371.2962109603.

The spelling of 51187221 in words is "fifty-one million, one hundred eighty-seven thousand, two hundred twenty-one".