51217920 has 400 divisors, whose sum is σ = 207955440. Its totient is φ = 11943936.

The previous prime is 51217891. The next prime is 51217927. The reversal of 51217920 is 2971215.

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 (51217927) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 2695671 + ... + 2695689.

Almost surely, 2^51217920 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 51217920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103977720).

51217920 is an abundant number, since it is smaller than the sum of its proper divisors (156737520).

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

51217920 is a wasteful number, since it uses less digits than its factorization.

51217920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67 (or 42 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 51217920 is about 7156.6696165186. The cubic root of 51217920 is about 371.3704231316.

It can be divided in two parts, 5121 and 7920, that added together give a triangular number (13041 = T₁₆₁).

The spelling of 51217920 in words is "fifty-one million, two hundred seventeen thousand, nine hundred twenty".