646974121 has 4 divisors (see below), whose sum is σ = 648245700. Its totient is φ = 645702544.

The previous prime is 646974101. The next prime is 646974157. The reversal of 646974121 is 121479646.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 121479646 = 2 ⋅60739823.

It can be written as a sum of positive squares in 2 ways, for example, as 208658025 + 438316096 = 14445^2 + 20936^2 .

It is a cyclic number.

It is not a de Polignac number, because 646974121 - 2⁹ = 646973609 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (646974101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 635026 + ... + 636043.

It is an arithmetic number, because the mean of its divisors is an integer number (162061425).

Almost surely, 2^646974121 is an apocalyptic number.

It is an amenable number.

646974121 is a deficient number, since it is larger than the sum of its proper divisors (1271579).

646974121 is a wasteful number, since it uses less digits than its factorization.

646974121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1271578.

The product of its digits is 72576, while the sum is 40.

The square root of 646974121 is about 25435.6859746302. The cubic root of 646974121 is about 864.8928424843.

The spelling of 646974121 in words is "six hundred forty-six million, nine hundred seventy-four thousand, one hundred twenty-one".