51649920 has 384 divisors, whose sum is σ = 216280800. Its totient is φ = 11612160.

The previous prime is 51649907. The next prime is 51649933. The reversal of 51649920 is 2994615.

51649920 is a `hidden beast` number, since 5 + 1 + 649 + 9 + 2 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (51649907) and next prime (51649933).

It is a tau number, because it is divible by the number of its divisors (384).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 846690 + ... + 846750.

Almost surely, 2^51649920 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 51649920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (108140400).

51649920 is an abundant number, since it is smaller than the sum of its proper divisors (164630880).

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

51649920 is a wasteful number, since it uses less digits than its factorization.

51649920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103 (or 78 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 51649920 is about 7186.7878777657. The cubic root of 51649920 is about 372.4116151426.

The spelling of 51649920 in words is "fifty-one million, six hundred forty-nine thousand, nine hundred twenty".