645216605414021 has 8 divisors (see below), whose sum is σ = 652465661353464. Its totient is φ = 637984427371200.

The previous prime is 645216605413999. The next prime is 645216605414053. The reversal of 645216605414021 is 120414506612546.

It can be written as a sum of positive squares in 4 ways, for example, as 364757476890625 + 280459128523396 = 19098625^2 + 16746914^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645216605414021 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645216605414321) 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, 4219397270 + ... + 4219550183.

It is an arithmetic number, because the mean of its divisors is an integer number (81558207669183).

Almost surely, 2^{645216605414021} is an apocalyptic number.

It is an amenable number.

645216605414021 is a deficient number, since it is larger than the sum of its proper divisors (7249055939443).

645216605414021 is a wasteful number, since it uses less digits than its factorization.

645216605414021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8438948311.

The product of its (nonzero) digits is 1382400, while the sum is 47.

The spelling of 645216605414021 in words is "six hundred forty-five trillion, two hundred sixteen billion, six hundred five million, four hundred fourteen thousand, twenty-one".