21421242531 has 32 divisors (see below), whose sum is σ = 34187469120. Its totient is φ = 13178011392.

The previous prime is 21421242529. The next prime is 21421242553. The reversal of 21421242531 is 13524212412.

21421242531 is a `hidden beast` number, since 2 + 1 + 4 + 2 + 124 + 2 + 531 = 666.

It is not a de Polignac number, because 21421242531 - 2¹ = 21421242529 is a prime.

It is a super-2 number, since 2×21421242531² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 21421242495 and 21421242504.

It is not an unprimeable number, because it can be changed into a prime (21421240531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1324711 + ... + 1340783.

It is an arithmetic number, because the mean of its divisors is an integer number (1068358410).

Almost surely, 2^21421242531 is an apocalyptic number.

21421242531 is a deficient number, since it is larger than the sum of its proper divisors (12766226589).

21421242531 is a wasteful number, since it uses less digits than its factorization.

21421242531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19892 (or 19886 counting only the distinct ones).

The product of its digits is 3840, while the sum is 27.

Adding to 21421242531 its reverse (13524212412), we get a palindrome (34945454943).

The spelling of 21421242531 in words is "twenty-one billion, four hundred twenty-one million, two hundred forty-two thousand, five hundred thirty-one".