21531236 has 24 divisors (see below), whose sum is σ = 39352320. Its totient is φ = 10296000.

The previous prime is 21531233. The next prime is 21531269. The reversal of 21531236 is 63213512.

It is not an unprimeable number, because it can be changed into a prime (21531233) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10061 + ... + 12011.

It is an arithmetic number, because the mean of its divisors is an integer number (1639680).

Almost surely, 2^21531236 is an apocalyptic number.

It is an amenable number.

21531236 is a deficient number, since it is larger than the sum of its proper divisors (17821084).

21531236 is a wasteful number, since it uses less digits than its factorization.

21531236 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2075 (or 2073 counting only the distinct ones).

The product of its digits is 1080, while the sum is 23.

The square root of 21531236 is about 4640.1762897545. The cubic root of 21531236 is about 278.1994841706.

Adding to 21531236 its reverse (63213512), we get a palindrome (84744748).

The spelling of 21531236 in words is "twenty-one million, five hundred thirty-one thousand, two hundred thirty-six".