21421321531 has 4 divisors (see below), whose sum is σ = 21422001672. Its totient is φ = 21420641392.

The previous prime is 21421321489. The next prime is 21421321543. The reversal of 21421321531 is 13512312412.

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

It is a cyclic number.

It is not a de Polignac number, because 21421321531 - 2¹³ = 21421313339 is a prime.

It is a super-2 number, since 2×21421321531² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21421321496 and 21421321505.

It is not an unprimeable number, because it can be changed into a prime (21421321931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 290410 + ... + 356623.

It is an arithmetic number, because the mean of its divisors is an integer number (5355500418).

Almost surely, 2^21421321531 is an apocalyptic number.

21421321531 is a deficient number, since it is larger than the sum of its proper divisors (680141).

21421321531 is an equidigital number, since it uses as much as digits as its factorization.

21421321531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 680140.

The product of its digits is 1440, while the sum is 25.

Adding to 21421321531 its reverse (13512312412), we get a palindrome (34933633943).

The spelling of 21421321531 in words is "twenty-one billion, four hundred twenty-one million, three hundred twenty-one thousand, five hundred thirty-one".