21155431213 has 8 divisors (see below), whose sum is σ = 24426890432. Its totient is φ = 17946285696.

The previous prime is 21155431189. The next prime is 21155431217. The reversal of 21155431213 is 31213455112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21155431213 - 2⁹ = 21155430701 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155431217) 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 7 ways as a sum of consecutive naturals, for example, 15577695 + ... + 15579052.

It is an arithmetic number, because the mean of its divisors is an integer number (3053361304).

Almost surely, 2^21155431213 is an apocalyptic number.

It is an amenable number.

21155431213 is a deficient number, since it is larger than the sum of its proper divisors (3271459219).

21155431213 is an equidigital number, since it uses as much as digits as its factorization.

21155431213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31156851.

The product of its digits is 3600, while the sum is 28.

Adding to 21155431213 its reverse (31213455112), we get a palindrome (52368886325).

The spelling of 21155431213 in words is "twenty-one billion, one hundred fifty-five million, four hundred thirty-one thousand, two hundred thirteen".