21621033 has 32 divisors (see below), whose sum is σ = 36915200. Its totient is φ = 12251088.

The previous prime is 21621029. The next prime is 21621053. The reversal of 21621033 is 33012612.

It is not a de Polignac number, because 21621033 - 2² = 21621029 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21620997 and 21621015.

It is not an unprimeable number, because it can be changed into a prime (21621013) 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, 25860 + ... + 26682.

It is an arithmetic number, because the mean of its divisors is an integer number (1153600).

Almost surely, 2^21621033 is an apocalyptic number.

It is an amenable number.

21621033 is a deficient number, since it is larger than the sum of its proper divisors (15294167).

21621033 is a wasteful number, since it uses less digits than its factorization.

21621033 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 978 (or 972 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

The square root of 21621033 is about 4649.8422553889. The cubic root of 21621033 is about 278.5856956345.

Adding to 21621033 its reverse (33012612), we get a palindrome (54633645).

The spelling of 21621033 in words is "twenty-one million, six hundred twenty-one thousand, thirty-three".