21155142421 has 8 divisors (see below), whose sum is σ = 24178207040. Its totient is φ = 18132303168.

The previous prime is 21155142409. The next prime is 21155142433. The reversal of 21155142421 is 12424155112.

It is an interprime number because it is at equal distance from previous prime (21155142409) and next prime (21155142433).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21155142421 - 2¹⁵ = 21155109653 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21155142421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155142521) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 273790 + ... + 342448.

It is an arithmetic number, because the mean of its divisors is an integer number (3022275880).

Almost surely, 2^21155142421 is an apocalyptic number.

It is an amenable number.

21155142421 is a deficient number, since it is larger than the sum of its proper divisors (3023064619).

21155142421 is an equidigital number, since it uses as much as digits as its factorization.

21155142421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112683.

The product of its digits is 3200, while the sum is 28.

Adding to 21155142421 its reverse (12424155112), we get a palindrome (33579297533).

The spelling of 21155142421 in words is "twenty-one billion, one hundred fifty-five million, one hundred forty-two thousand, four hundred twenty-one".