65691990 has 144 divisors (see below), whose sum is σ = 211711968. Its totient is φ = 13837824.

The previous prime is 65691953. The next prime is 65691991. The reversal of 65691990 is 9919656.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (65691991) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 106162 + ... + 106778.

It is an arithmetic number, because the mean of its divisors is an integer number (1470222).

Almost surely, 2^65691990 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 65691990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105855984).

65691990 is an abundant number, since it is smaller than the sum of its proper divisors (146019978).

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

65691990 is a wasteful number, since it uses less digits than its factorization.

65691990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 663 (or 647 counting only the distinct ones).

The product of its (nonzero) digits is 131220, while the sum is 45.

The square root of 65691990 is about 8105.0595309350. The cubic root of 65691990 is about 403.4943638282.

The spelling of 65691990 in words is "sixty-five million, six hundred ninety-one thousand, nine hundred ninety".