9921621961 has 2 divisors, whose sum is σ = 9921621962. Its totient is φ = 9921621960.

The previous prime is 9921621949. The next prime is 9921622019. The reversal of 9921621961 is 1691261299.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 8903054736 + 1018567225 = 94356^2 + 31915^2 .

It is a cyclic number.

It is not a de Polignac number, because 9921621961 - 2²¹ = 9919524809 is a prime.

It is not a weakly prime, because it can be changed into another prime (9921621361) by changing a digit.

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, 4960810980 + 4960810981.

It is an arithmetic number, because the mean of its divisors is an integer number (4960810981).

Almost surely, 2^9921621961 is an apocalyptic number.

It is an amenable number.

9921621961 is a deficient number, since it is larger than the sum of its proper divisors (1).

9921621961 is an equidigital number, since it uses as much as digits as its factorization.

9921621961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 104976, while the sum is 46.

The square root of 9921621961 is about 99607.3388912684. The cubic root of 9921621961 is about 2148.7912412970.

The spelling of 9921621961 in words is "nine billion, nine hundred twenty-one million, six hundred twenty-one thousand, nine hundred sixty-one".