21621633 has 32 divisors (see below), whose sum is σ = 33426432. Its totient is φ = 12302400.

The previous prime is 21621631. The next prime is 21621641. The reversal of 21621633 is 33612612.

It is a happy number.

It is not a de Polignac number, because 21621633 - 2¹ = 21621631 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21621631) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 46066 + ... + 46532.

It is an arithmetic number, because the mean of its divisors is an integer number (1044576).

Almost surely, 2^21621633 is an apocalyptic number.

21621633 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

21621633 is a deficient number, since it is larger than the sum of its proper divisors (11804799).

21621633 is a wasteful number, since it uses less digits than its factorization.

21621633 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 565.

The product of its digits is 1296, while the sum is 24.

The square root of 21621633 is about 4649.9067732590. The cubic root of 21621633 is about 278.5882725985.

The spelling of 21621633 in words is "twenty-one million, six hundred twenty-one thousand, six hundred thirty-three".