21531339 has 10 divisors (see below), whose sum is σ = 32164220. Its totient is φ = 14354172.

The previous prime is 21531337. The next prime is 21531343. The reversal of 21531339 is 93313512.

It is a happy number.

It is not a de Polignac number, because 21531339 - 2¹ = 21531337 is a prime.

It is a super-3 number, since 3×21531339³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21531337) 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 9 ways as a sum of consecutive naturals, for example, 132829 + ... + 132990.

It is an arithmetic number, because the mean of its divisors is an integer number (3216422).

Almost surely, 2^21531339 is an apocalyptic number.

21531339 is a deficient number, since it is larger than the sum of its proper divisors (10632881).

21531339 is an equidigital number, since it uses as much as digits as its factorization.

21531339 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 265831 (or 265822 counting only the distinct ones).

The product of its digits is 2430, while the sum is 27.

The square root of 21531339 is about 4640.1873884575. The cubic root of 21531339 is about 278.1999277819.

The spelling of 21531339 in words is "twenty-one million, five hundred thirty-one thousand, three hundred thirty-nine".