21142531 has 2 divisors, whose sum is σ = 21142532. Its totient is φ = 21142530.

The previous prime is 21142529. The next prime is 21142613. The reversal of 21142531 is 13524112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21142531 - 2¹ = 21142529 is a prime.

It is a super-2 number, since 2×21142531² = 894013234171922, which contains 22 as substring.

Together with 21142529, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21142499 and 21142508.

It is not a weakly prime, because it can be changed into another prime (21142831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10571265 + 10571266.

It is an arithmetic number, because the mean of its divisors is an integer number (10571266).

Almost surely, 2^21142531 is an apocalyptic number.

21142531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21142531 is an equidigital number, since it uses as much as digits as its factorization.

21142531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 240, while the sum is 19.

The square root of 21142531 is about 4598.1008035927. The cubic root of 21142531 is about 276.5151889300.

Adding to 21142531 its reverse (13524112), we get a palindrome (34666643).

The spelling of 21142531 in words is "twenty-one million, one hundred forty-two thousand, five hundred thirty-one".