65721605 has 8 divisors (see below), whose sum is σ = 79752600. Its totient is φ = 51986176.

The previous prime is 65721599. The next prime is 65721619. The reversal of 65721605 is 50612756.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 2455489 + 63266116 = 1567^2 + 7954^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 65721605 - 2⁸ = 65721349 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 73400 + ... + 74289.

It is an arithmetic number, because the mean of its divisors is an integer number (9969075).

Almost surely, 2^65721605 is an apocalyptic number.

It is an amenable number.

65721605 is a deficient number, since it is larger than the sum of its proper divisors (14030995).

65721605 is a wasteful number, since it uses less digits than its factorization.

65721605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 147783.

The product of its (nonzero) digits is 12600, while the sum is 32.

The square root of 65721605 is about 8106.8862703260. The cubic root of 65721605 is about 403.5549886236.

The spelling of 65721605 in words is "sixty-five million, seven hundred twenty-one thousand, six hundred five".