21531369 has 16 divisors (see below), whose sum is σ = 29822400. Its totient is φ = 13801536.

The previous prime is 21531361. The next prime is 21531379. The reversal of 21531369 is 96313512.

It is not a de Polignac number, because 21531369 - 2³ = 21531361 is a prime.

It is a super-2 number, since 2×21531369² = 927199702028322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21531361) 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, 32647 + ... + 33299.

It is an arithmetic number, because the mean of its divisors is an integer number (1863900).

Almost surely, 2^21531369 is an apocalyptic number.

21531369 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21531369 is a deficient number, since it is larger than the sum of its proper divisors (8291031).

21531369 is a wasteful number, since it uses less digits than its factorization.

21531369 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1064.

The product of its digits is 4860, while the sum is 30.

The square root of 21531369 is about 4640.1906210844. The cubic root of 21531369 is about 278.2000569889.

The spelling of 21531369 in words is "twenty-one million, five hundred thirty-one thousand, three hundred sixty-nine".