721695766665 has 16 divisors (see below), whose sum is σ = 1156640976000. Its totient is φ = 384261825792.

The previous prime is 721695766663. The next prime is 721695766717. The reversal of 721695766665 is 566667596127.

It is not a de Polignac number, because 721695766665 - 2¹ = 721695766663 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 721695766596 and 721695766605.

It is not an unprimeable number, because it can be changed into a prime (721695766663) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 40152160 + ... + 40170129.

It is an arithmetic number, because the mean of its divisors is an integer number (72290061000).

Almost surely, 2^721695766665 is an apocalyptic number.

It is an amenable number.

721695766665 is a deficient number, since it is larger than the sum of its proper divisors (434945209335).

721695766665 is a wasteful number, since it uses less digits than its factorization.

721695766665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80322896.

The product of its digits is 171460800, while the sum is 66.

The spelling of 721695766665 in words is "seven hundred twenty-one billion, six hundred ninety-five million, seven hundred sixty-six thousand, six hundred sixty-five".