664651242620021 has 8 divisors (see below), whose sum is σ = 670578325305984. Its totient is φ = 658724953149760.

The previous prime is 664651242620009. The next prime is 664651242620077. The reversal of 664651242620021 is 120026242156466.

It is a happy number.

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 664651242620021 - 2¹⁰ = 664651242618997 is a prime.

It is a super-2 number, since 2×664651242620021² (a number of 30 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664651242610021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 196620551 + ... + 199972356.

It is an arithmetic number, because the mean of its divisors is an integer number (83822290663248).

Almost surely, 2^{664651242620021} is an apocalyptic number.

It is an amenable number.

664651242620021 is a deficient number, since it is larger than the sum of its proper divisors (5927082685963).

664651242620021 is a wasteful number, since it uses less digits than its factorization.

664651242620021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 396607851.

The product of its (nonzero) digits is 1658880, while the sum is 47.

Adding to 664651242620021 its reverse (120026242156466), we get a palindrome (784677484776487).

The spelling of 664651242620021 in words is "six hundred sixty-four trillion, six hundred fifty-one billion, two hundred forty-two million, six hundred twenty thousand, twenty-one".