21506633 has 4 divisors (see below), whose sum is σ = 22441728. Its totient is φ = 20571540.

The previous prime is 21506629. The next prime is 21506647. The reversal of 21506633 is 33660512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21506633 - 2² = 21506629 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21506333) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 467513 + ... + 467558.

It is an arithmetic number, because the mean of its divisors is an integer number (5610432).

Almost surely, 2^21506633 is an apocalyptic number.

21506633 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

21506633 is a deficient number, since it is larger than the sum of its proper divisors (935095).

21506633 is an equidigital number, since it uses as much as digits as its factorization.

21506633 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 935094.

The product of its (nonzero) digits is 3240, while the sum is 26.

The square root of 21506633 is about 4637.5244473749. The cubic root of 21506633 is about 278.0934808030.

The spelling of 21506633 in words is "twenty-one million, five hundred six thousand, six hundred thirty-three".