664726121 has 4 divisors (see below), whose sum is σ = 680184912. Its totient is φ = 649267332.

The previous prime is 664726109. The next prime is 664726141. The reversal of 664726121 is 121627466.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 121627466 = 2 ⋅60813733.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-664726121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664726141) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7729331 + ... + 7729416.

It is an arithmetic number, because the mean of its divisors is an integer number (170046228).

Almost surely, 2^664726121 is an apocalyptic number.

It is an amenable number.

664726121 is a deficient number, since it is larger than the sum of its proper divisors (15458791).

664726121 is a wasteful number, since it uses less digits than its factorization.

664726121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15458790.

The product of its digits is 24192, while the sum is 35.

The square root of 664726121 is about 25782.2830835440. The cubic root of 664726121 is about 872.7320295968.

It can be divided in two parts, 6647 and 26121, that added together give a 15-th power (32768 = 2¹⁵).

The spelling of 664726121 in words is "six hundred sixty-four million, seven hundred twenty-six thousand, one hundred twenty-one".