21221199973 has 2 divisors, whose sum is σ = 21221199974. Its totient is φ = 21221199972.

The previous prime is 21221199949. The next prime is 21221200027. The reversal of 21221199973 is 37999112212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11188773729 + 10032426244 = 105777^2 + 100162^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21221199973 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21221199073) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610599986 + 10610599987.

It is an arithmetic number, because the mean of its divisors is an integer number (10610599987).

Almost surely, 2^21221199973 is an apocalyptic number.

It is an amenable number.

21221199973 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221199973 is an equidigital number, since it uses as much as digits as its factorization.

21221199973 is an evil number, because the sum of its binary digits is even.

The product of its digits is 122472, while the sum is 46.

The spelling of 21221199973 in words is "twenty-one billion, two hundred twenty-one million, one hundred ninety-nine thousand, nine hundred seventy-three".