65981556 has 72 divisors (see below), whose sum is σ = 178161984. Its totient is φ = 20517120.

The previous prime is 65981551. The next prime is 65981563. The reversal of 65981556 is 65518956.

It is a happy number.

65981556 is a `hidden beast` number, since 6 + 5 + 98 + 1 + 556 = 666.

It is a super-2 number, since 2×65981556² = 8707131464362272, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (65981551) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 79761 + ... + 80583.

It is an arithmetic number, because the mean of its divisors is an integer number (2474472).

Almost surely, 2^65981556 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 65981556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (89080992).

65981556 is an abundant number, since it is smaller than the sum of its proper divisors (112180428).

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

65981556 is a wasteful number, since it uses less digits than its factorization.

65981556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 981 (or 976 counting only the distinct ones).

The product of its digits is 324000, while the sum is 45.

The square root of 65981556 is about 8122.9031755894. The cubic root of 65981556 is about 404.0863537919.

It can be divided in two parts, 659 and 81556, that added together give a triangular number (82215 = T₄₀₅).

The spelling of 65981556 in words is "sixty-five million, nine hundred eighty-one thousand, five hundred fifty-six".