51689840 has 80 divisors (see below), whose sum is σ = 124867008. Its totient is φ = 19888128.

The previous prime is 51689831. The next prime is 51689857. The reversal of 51689840 is 4898615.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 309437 + ... + 309603.

Almost surely, 2^51689840 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 51689840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (62433504).

51689840 is an abundant number, since it is smaller than the sum of its proper divisors (73177168).

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

51689840 is a wasteful number, since it uses less digits than its factorization.

51689840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 306 (or 300 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 41.

The square root of 51689840 is about 7189.5646599777. The cubic root of 51689840 is about 372.5075355441.

The spelling of 51689840 in words is "fifty-one million, six hundred eighty-nine thousand, eight hundred forty".