21201219997 has 2 divisors, whose sum is σ = 21201219998. Its totient is φ = 21201219996.

The previous prime is 21201219953. The next prime is 21201220031. The reversal of 21201219997 is 79991210212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18168074521 + 3033145476 = 134789^2 + 55074^2 .

It is a cyclic number.

It is not a de Polignac number, because 21201219997 - 2²⁷ = 21067002269 is a prime.

It is a super-2 number, since 2×21201219997² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21201219937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10600609998 + 10600609999.

It is an arithmetic number, because the mean of its divisors is an integer number (10600609999).

Almost surely, 2^21201219997 is an apocalyptic number.

It is an amenable number.

21201219997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201219997 is an equidigital number, since it uses as much as digits as its factorization.

21201219997 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40824, while the sum is 43.

The spelling of 21201219997 in words is "twenty-one billion, two hundred one million, two hundred nineteen thousand, nine hundred ninety-seven".