21423240021 has 8 divisors (see below), whose sum is σ = 28571536384. Its totient is φ = 14278551840.

The previous prime is 21423240001. The next prime is 21423240023. The reversal of 21423240021 is 12004232412.

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

It is not a de Polignac number, because 21423240021 - 2⁵ = 21423239989 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 21423240021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21423240023) 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, 888160 + ... + 911961.

It is an arithmetic number, because the mean of its divisors is an integer number (3571442048).

Almost surely, 2^21423240021 is an apocalyptic number.

It is an amenable number.

21423240021 is a deficient number, since it is larger than the sum of its proper divisors (7148296363).

21423240021 is a wasteful number, since it uses less digits than its factorization.

21423240021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1804091.

The product of its (nonzero) digits is 768, while the sum is 21.

Adding to 21423240021 its reverse (12004232412), we get a palindrome (33427472433).

The spelling of 21423240021 in words is "twenty-one billion, four hundred twenty-three million, two hundred forty thousand, twenty-one".