21213404502421 has 4 divisors (see below), whose sum is σ = 21213971606700. Its totient is φ = 21212837398144.

The previous prime is 21213404502419. The next prime is 21213404502427. The reversal of 21213404502421 is 12420540431212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6682716159025 + 14530688343396 = 2585095^2 + 3811914^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213404502421 - 2¹ = 21213404502419 is a prime.

It is a super-2 number, since 2×21213404502421² (a number of 27 digits) contains 22 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 (21213404502427) 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, 283496026 + ... + 283570843.

It is an arithmetic number, because the mean of its divisors is an integer number (5303492901675).

Almost surely, 2^{21213404502421} is an apocalyptic number.

It is an amenable number.

21213404502421 is a deficient number, since it is larger than the sum of its proper divisors (567104279).

21213404502421 is an equidigital number, since it uses as much as digits as its factorization.

21213404502421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 567104278.

The product of its (nonzero) digits is 15360, while the sum is 31.

Adding to 21213404502421 its reverse (12420540431212), we get a palindrome (33633944933633).

The spelling of 21213404502421 in words is "twenty-one trillion, two hundred thirteen billion, four hundred four million, five hundred two thousand, four hundred twenty-one".