21002121210997 has 2 divisors, whose sum is σ = 21002121210998. Its totient is φ = 21002121210996.

The previous prime is 21002121210991. The next prime is 21002121211033. The reversal of 21002121210997 is 79901212120012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18873889559281 + 2128231651716 = 4344409^2 + 1458846^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21002121210997 is a prime.

It is a super-2 number, since 2×21002121210997² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21002121210991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501060605498 + 10501060605499.

It is an arithmetic number, because the mean of its divisors is an integer number (10501060605499).

Almost surely, 2^{21002121210997} is an apocalyptic number.

It is an amenable number.

21002121210997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002121210997 is an equidigital number, since it uses as much as digits as its factorization.

21002121210997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9072, while the sum is 37.

The spelling of 21002121210997 in words is "twenty-one trillion, two billion, one hundred twenty-one million, two hundred ten thousand, nine hundred ninety-seven".