21993621413 has 2 divisors, whose sum is σ = 21993621414. Its totient is φ = 21993621412.

The previous prime is 21993621379. The next prime is 21993621421. The reversal of 21993621413 is 31412639912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18289316644 + 3704304769 = 135238^2 + 60863^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21993621413 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21993621473) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10996810706 + 10996810707.

It is an arithmetic number, because the mean of its divisors is an integer number (10996810707).

Almost surely, 2^21993621413 is an apocalyptic number.

It is an amenable number.

21993621413 is a deficient number, since it is larger than the sum of its proper divisors (1).

21993621413 is an equidigital number, since it uses as much as digits as its factorization.

21993621413 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69984, while the sum is 41.

The spelling of 21993621413 in words is "twenty-one billion, nine hundred ninety-three million, six hundred twenty-one thousand, four hundred thirteen".