20993439901 has 6 divisors (see below), whose sum is σ = 24420940350. Its totient is φ = 17994377016.

The previous prime is 20993439899. The next prime is 20993439917. The reversal of 20993439901 is 10993439902.

It can be written as a sum of positive squares in only one way, i.e., 19418143801 + 1575296100 = 139349^2 + 39690^2 .

It is not a de Polignac number, because 20993439901 - 2¹ = 20993439899 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (49), and also a Moran number because the ratio is a prime number: 428437549 = 20993439901 / (2 + 0 + 9 + 9 + 3 + 4 + 3 + 9 + 9 + 0 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20993479901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 214218726 + ... + 214218823.

It is an arithmetic number, because the mean of its divisors is an integer number (4070156725).

Almost surely, 2^20993439901 is an apocalyptic number.

It is an amenable number.

20993439901 is a deficient number, since it is larger than the sum of its proper divisors (3427500449).

20993439901 is an equidigital number, since it uses as much as digits as its factorization.

20993439901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 428437563 (or 428437556 counting only the distinct ones).

The product of its (nonzero) digits is 472392, while the sum is 49.

Subtracting from 20993439901 its reverse (10993439902), we obtain a palindrome (9999999999).

The spelling of 20993439901 in words is "twenty billion, nine hundred ninety-three million, four hundred thirty-nine thousand, nine hundred one".