21329931 has 16 divisors (see below), whose sum is σ = 33037568. Its totient is φ = 11988000.

The previous prime is 21329929. The next prime is 21329939. The reversal of 21329931 is 13992312.

It is a happy number.

It is not a de Polignac number, because 21329931 - 2¹ = 21329929 is a prime.

It is a super-2 number, since 2×21329931² = 909931912929522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21329939) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7045 + ... + 9606.

It is an arithmetic number, because the mean of its divisors is an integer number (2064848).

Almost surely, 2^21329931 is an apocalyptic number.

21329931 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21329931 is a deficient number, since it is larger than the sum of its proper divisors (11707637).

21329931 is a wasteful number, since it uses less digits than its factorization.

21329931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16722.

The product of its digits is 2916, while the sum is 30.

The square root of 21329931 is about 4618.4338254434. The cubic root of 21329931 is about 277.3297649178.

The spelling of 21329931 in words is "twenty-one million, three hundred twenty-nine thousand, nine hundred thirty-one".