21353131 has 16 divisors (see below), whose sum is σ = 23696640. Its totient is φ = 19150560.

The previous prime is 21353119. The next prime is 21353153. The reversal of 21353131 is 13135312.

It is a cyclic number.

It is not a de Polignac number, because 21353131 - 2⁹ = 21352619 is a prime.

It is a super-2 number, since 2×21353131² = 911912407006322, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21353099 and 21353108.

It is not an unprimeable number, because it can be changed into a prime (21353191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 57061 + ... + 57433.

It is an arithmetic number, because the mean of its divisors is an integer number (1481040).

Almost surely, 2^21353131 is an apocalyptic number.

21353131 is a deficient number, since it is larger than the sum of its proper divisors (2343509).

21353131 is a wasteful number, since it uses less digits than its factorization.

21353131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546.

The product of its digits is 270, while the sum is 19.

The square root of 21353131 is about 4620.9448168097. The cubic root of 21353131 is about 277.4302765609.

Adding to 21353131 its reverse (13135312), we get a palindrome (34488443).

It can be divided in two parts, 213 and 53131, that multiplied together give a triangular number (11316903 = T₄₇₅₇).

The spelling of 21353131 in words is "twenty-one million, three hundred fifty-three thousand, one hundred thirty-one".