20821278389 has 4 divisors (see below), whose sum is σ = 20937598560. Its totient is φ = 20704958220.

The previous prime is 20821278353. The next prime is 20821278397. The reversal of 20821278389 is 98387212802.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20821278389 is a prime.

It is a super-3 number, since 3×20821278389³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20821278319) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 58159817 + ... + 58160174.

It is an arithmetic number, because the mean of its divisors is an integer number (5234399640).

Almost surely, 2^20821278389 is an apocalyptic number.

It is an amenable number.

20821278389 is a deficient number, since it is larger than the sum of its proper divisors (116320171).

20821278389 is a wasteful number, since it uses less digits than its factorization.

20821278389 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116320170.

The product of its (nonzero) digits is 774144, while the sum is 50.

The spelling of 20821278389 in words is "twenty billion, eight hundred twenty-one million, two hundred seventy-eight thousand, three hundred eighty-nine".