21533506 has 16 divisors (see below), whose sum is σ = 32853888. Its totient is φ = 10584000.

The previous prime is 21533471. The next prime is 21533507. The reversal of 21533506 is 60533512.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21533507) 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, 33811 + ... + 34441.

It is an arithmetic number, because the mean of its divisors is an integer number (2053368).

Almost surely, 2^21533506 is an apocalyptic number.

21533506 is a deficient number, since it is larger than the sum of its proper divisors (11320382).

21533506 is a wasteful number, since it uses less digits than its factorization.

21533506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 897.

The product of its (nonzero) digits is 2700, while the sum is 25.

The square root of 21533506 is about 4640.4208860835. The cubic root of 21533506 is about 278.2092605197.

The spelling of 21533506 in words is "twenty-one million, five hundred thirty-three thousand, five hundred six".