6491228788521 has 27 divisors (see below), whose sum is σ = 9446682381591. Its totient is φ = 4295205372384.

The previous prime is 6491228788487. The next prime is 6491228788579. The reversal of 6491228788521 is 1258878221946.

The square root of 6491228788521 is 2547789.

It is a perfect power (a square), and thus also a powerful number.

6491228788521 is a `hidden beast` number, since 6 + 4 + 9 + 1 + 2 + 28 + 7 + 88 + 521 = 666.

It can be written as a sum of positive squares in only one way, i.e., 3812978709225 + 2678250079296 = 1952685^2 + 1636536^2 .

It is a de Polignac number, because none of the positive numbers 2^k-6491228788521 is a prime.

It is not an unprimeable number, because it can be changed into a prime (6491228788921) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 1047138180 + ... + 1047144378.

Almost surely, 2^{6491228788521} is an apocalyptic number.

6491228788521 is the 2547789-th square number.

6491228788521 is the 1273895-th centered octagonal number.

It is an amenable number.

6491228788521 is a deficient number, since it is larger than the sum of its proper divisors (2955453593070).

6491228788521 is an frugal number, since it uses more digits than its factorization.

6491228788521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12678 (or 6339 counting only the distinct ones).

The product of its digits is 30965760, while the sum is 63.

The spelling of 6491228788521 in words is "six trillion, four hundred ninety-one billion, two hundred twenty-eight million, seven hundred eighty-eight thousand, five hundred twenty-one".