20921221949 has 2 divisors, whose sum is σ = 20921221950. Its totient is φ = 20921221948.

The previous prime is 20921221931. The next prime is 20921221969. The reversal of 20921221949 is 94912212902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10533943225 + 10387278724 = 102635^2 + 101918^2 .

It is a cyclic number.

It is not a de Polignac number, because 20921221949 - 2⁸ = 20921221693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20921221969) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10460610974 + 10460610975.

It is an arithmetic number, because the mean of its divisors is an integer number (10460610975).

Almost surely, 2^20921221949 is an apocalyptic number.

It is an amenable number.

20921221949 is a deficient number, since it is larger than the sum of its proper divisors (1).

20921221949 is an equidigital number, since it uses as much as digits as its factorization.

20921221949 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 46656, while the sum is 41.

The spelling of 20921221949 in words is "twenty billion, nine hundred twenty-one million, two hundred twenty-one thousand, nine hundred forty-nine".