21155320421 has 24 divisors (see below), whose sum is σ = 23201881920. Its totient is φ = 19221805440.

The previous prime is 21155320411. The next prime is 21155320451. The reversal of 21155320421 is 12402355112.

It is not a de Polignac number, because 21155320421 - 2¹⁸ = 21155058277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155320411) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7954790 + ... + 7957448.

It is an arithmetic number, because the mean of its divisors is an integer number (966745080).

Almost surely, 2^21155320421 is an apocalyptic number.

It is an amenable number.

21155320421 is a deficient number, since it is larger than the sum of its proper divisors (2046561499).

21155320421 is a wasteful number, since it uses less digits than its factorization.

21155320421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3225 (or 3194 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 26.

Adding to 21155320421 its reverse (12402355112), we get a palindrome (33557675533).

The spelling of 21155320421 in words is "twenty-one billion, one hundred fifty-five million, three hundred twenty thousand, four hundred twenty-one".