21621433 has 4 divisors (see below), whose sum is σ = 22893300. Its totient is φ = 20349568.

The previous prime is 21621427. The next prime is 21621437. The reversal of 21621433 is 33412612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9566649 + 12054784 = 3093^2 + 3472^2 .

It is a cyclic number.

It is not a de Polignac number, because 21621433 - 2⁵ = 21621401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21621437) 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, 635908 + ... + 635941.

It is an arithmetic number, because the mean of its divisors is an integer number (5723325).

Almost surely, 2^21621433 is an apocalyptic number.

It is an amenable number.

21621433 is a deficient number, since it is larger than the sum of its proper divisors (1271867).

21621433 is a wasteful number, since it uses less digits than its factorization.

21621433 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1271866.

The product of its digits is 864, while the sum is 22.

The square root of 21621433 is about 4649.8852674018. The cubic root of 21621433 is about 278.5874136158.

The spelling of 21621433 in words is "twenty-one million, six hundred twenty-one thousand, four hundred thirty-three".