21120019961 has 2 divisors, whose sum is σ = 21120019962. Its totient is φ = 21120019960.

The previous prime is 21120019937. The next prime is 21120020029. The reversal of 21120019961 is 16991002112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11605968361 + 9514051600 = 107731^2 + 97540^2 .

It is a cyclic number.

It is not a de Polignac number, because 21120019961 - 2²² = 21115825657 is a prime.

It is not a weakly prime, because it can be changed into another prime (21120013961) 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, 10560009980 + 10560009981.

It is an arithmetic number, because the mean of its divisors is an integer number (10560009981).

Almost surely, 2^21120019961 is an apocalyptic number.

It is an amenable number.

21120019961 is a deficient number, since it is larger than the sum of its proper divisors (1).

21120019961 is an equidigital number, since it uses as much as digits as its factorization.

21120019961 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 32.

The spelling of 21120019961 in words is "twenty-one billion, one hundred twenty million, nineteen thousand, nine hundred sixty-one".