645215263621556 has 6 divisors (see below), whose sum is σ = 1129126711337730. Its totient is φ = 322607631810776.

The previous prime is 645215263621529. The next prime is 645215263621583. The reversal of 645215263621556 is 655126362512546.

It is an interprime number because it is at equal distance from previous prime (645215263621529) and next prime (645215263621583).

It can be written as a sum of positive squares in only one way, i.e., 625736016560656 + 19479247060900 = 25014716^2 + 4413530^2 .

It is a super-2 number, since 2×645215263621556² (a number of 30 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 645215263621495 and 645215263621504.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80651907952691 + ... + 80651907952698.

It is an arithmetic number, because the mean of its divisors is an integer number (188187785222955).

Almost surely, 2^{645215263621556} is an apocalyptic number.

It is an amenable number.

645215263621556 is a deficient number, since it is larger than the sum of its proper divisors (483911447716174).

645215263621556 is a wasteful number, since it uses less digits than its factorization.

645215263621556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161303815905393 (or 161303815905391 counting only the distinct ones).

The product of its digits is 77760000, while the sum is 59.

The spelling of 645215263621556 in words is "six hundred forty-five trillion, two hundred fifteen billion, two hundred sixty-three million, six hundred twenty-one thousand, five hundred fifty-six".