21642243661421 has 4 divisors (see below), whose sum is σ = 21642359526144. Its totient is φ = 21642127796700.

The previous prime is 21642243661387. The next prime is 21642243661429. The reversal of 21642243661421 is 12416634224612.

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-21642243661421 is a prime.

It is a super-4 number, since 4×21642243661421⁴ (a number of 54 digits) contains 4444 as substring. Note that it is a super-d number also for d = 3.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21642243661429) 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, 57651725 + ... + 58025906.

It is an arithmetic number, because the mean of its divisors is an integer number (5410589881536).

Almost surely, 2^{21642243661421} is an apocalyptic number.

It is an amenable number.

21642243661421 is a deficient number, since it is larger than the sum of its proper divisors (115864723).

21642243661421 is a wasteful number, since it uses less digits than its factorization.

21642243661421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115864722.

The product of its digits is 663552, while the sum is 44.

The spelling of 21642243661421 in words is "twenty-one trillion, six hundred forty-two billion, two hundred forty-three million, six hundred sixty-one thousand, four hundred twenty-one".