998661262720021 has 2 divisors, whose sum is σ = 998661262720022. Its totient is φ = 998661262720020.

The previous prime is 998661262720007. The next prime is 998661262720081. The reversal of 998661262720021 is 120027262166899.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 748611242499121 + 250050020220900 = 27360761^2 + 15812970^2 .

It is an emirp because it is prime and its reverse (120027262166899) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 998661262720021 - 2³¹ = 998659115236373 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (998661262720081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499330631360010 + 499330631360011.

It is an arithmetic number, because the mean of its divisors is an integer number (499330631360011).

Almost surely, 2^{998661262720021} is an apocalyptic number.

It is an amenable number.

998661262720021 is a deficient number, since it is larger than the sum of its proper divisors (1).

998661262720021 is an equidigital number, since it uses as much as digits as its factorization.

998661262720021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15676416, while the sum is 61.

The spelling of 998661262720021 in words is "nine hundred ninety-eight trillion, six hundred sixty-one billion, two hundred sixty-two million, seven hundred twenty thousand, twenty-one".