7721784121 has 2 divisors, whose sum is σ = 7721784122. Its totient is φ = 7721784120.

The previous prime is 7721784071. The next prime is 7721784157. The reversal of 7721784121 is 1214871277.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7214633721 + 507150400 = 84939^2 + 22520^2 .

It is a cyclic number.

It is not a de Polignac number, because 7721784121 - 2¹¹ = 7721782073 is a prime.

It is a super-2 number, since 2×7721784121² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (7721781121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3860892060 + 3860892061.

It is an arithmetic number, because the mean of its divisors is an integer number (3860892061).

Almost surely, 2^7721784121 is an apocalyptic number.

It is an amenable number.

7721784121 is a deficient number, since it is larger than the sum of its proper divisors (1).

7721784121 is an equidigital number, since it uses as much as digits as its factorization.

7721784121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 43904, while the sum is 40.

The square root of 7721784121 is about 87873.6827554189. The cubic root of 7721784121 is about 1976.5412630497.

The spelling of 7721784121 in words is "seven billion, seven hundred twenty-one million, seven hundred eighty-four thousand, one hundred twenty-one".