6999215621 has 2 divisors, whose sum is σ = 6999215622. Its totient is φ = 6999215620.

The previous prime is 6999215609. The next prime is 6999215647. The reversal of 6999215621 is 1265129996.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5142467521 + 1856748100 = 71711^2 + 43090^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6999215621 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 6999215621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6999215021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3499607810 + 3499607811.

It is an arithmetic number, because the mean of its divisors is an integer number (3499607811).

Almost surely, 2^6999215621 is an apocalyptic number.

It is an amenable number.

6999215621 is a deficient number, since it is larger than the sum of its proper divisors (1).

6999215621 is an equidigital number, since it uses as much as digits as its factorization.

6999215621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 524880, while the sum is 50.

The square root of 6999215621 is about 83661.3149609782. The cubic root of 6999215621 is about 1912.8597294821.

The spelling of 6999215621 in words is "six billion, nine hundred ninety-nine million, two hundred fifteen thousand, six hundred twenty-one".