21212131 has 2 divisors, whose sum is σ = 21212132. Its totient is φ = 21212130.

The previous prime is 21212119. The next prime is 21212143. The reversal of 21212131 is 13121212.

It is a balanced prime because it is at equal distance from previous prime (21212119) and next prime (21212143).

It is a cyclic number.

It is not a de Polignac number, because 21212131 - 2⁵ = 21212099 is a prime.

It is a super-2 number, since 2×21212131² = 899909003122322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21212101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606065 + 10606066.

It is an arithmetic number, because the mean of its divisors is an integer number (10606066).

Almost surely, 2^21212131 is an apocalyptic number.

21212131 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212131 is an equidigital number, since it uses as much as digits as its factorization.

21212131 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24, while the sum is 13.

The square root of 21212131 is about 4605.6629273102. The cubic root of 21212131 is about 276.8182806361.

Adding to 21212131 its reverse (13121212), we get a palindrome (34333343).

It can be divided in two parts, 212121 and 31, that multiplied together give a triangular number (6575751 = T₃₆₂₆).

The spelling of 21212131 in words is "twenty-one million, two hundred twelve thousand, one hundred thirty-one".