64812121921 has 4 divisors (see below), whose sum is σ = 65540348100. Its totient is φ = 64083895744.

The previous prime is 64812121873. The next prime is 64812121961. The reversal of 64812121921 is 12912121846.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 27902027521 + 36910094400 = 167039^2 + 192120^2 .

It is a cyclic number.

It is not a de Polignac number, because 64812121921 - 2¹¹ = 64812119873 is a prime.

It is a super-2 number, since 2×64812121921² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (64812121961) 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, 364112956 + ... + 364113133.

It is an arithmetic number, because the mean of its divisors is an integer number (16385087025).

Almost surely, 2^64812121921 is an apocalyptic number.

It is an amenable number.

64812121921 is a deficient number, since it is larger than the sum of its proper divisors (728226179).

64812121921 is an equidigital number, since it uses as much as digits as its factorization.

64812121921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 728226178.

The product of its digits is 13824, while the sum is 37.

The spelling of 64812121921 in words is "sixty-four billion, eight hundred twelve million, one hundred twenty-one thousand, nine hundred twenty-one".