51981564 has 48 divisors (see below), whose sum is σ = 127169280. Its totient is φ = 16494720.

The previous prime is 51981557. The next prime is 51981581. The reversal of 51981564 is 46518915.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors.

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, 91072 + ... + 91640.

It is an arithmetic number, because the mean of its divisors is an integer number (2649360).

Almost surely, 2^51981564 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 51981564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (63584640).

51981564 is an abundant number, since it is smaller than the sum of its proper divisors (75187716).

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

51981564 is a wasteful number, since it uses less digits than its factorization.

51981564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 930 (or 928 counting only the distinct ones).

The product of its digits is 43200, while the sum is 39.

The square root of 51981564 is about 7209.8241310035. The cubic root of 51981564 is about 373.2069998423.

The spelling of 51981564 in words is "fifty-one million, nine hundred eighty-one thousand, five hundred sixty-four".