21621330 has 40 divisors (see below), whose sum is σ = 58139532. Its totient is φ = 5765472.

The previous prime is 21621329. The next prime is 21621337. The reversal of 21621330 is 3312612.

It can be written as a sum of positive squares in 2 ways, for example, as 17665209 + 3956121 = 4203^2 + 1989^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21621337) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 12537 + ... + 14156.

Almost surely, 2^21621330 is an apocalyptic number.

21621330 is an abundant number, since it is smaller than the sum of its proper divisors (36518202).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21621330 is a wasteful number, since it uses less digits than its factorization.

21621330 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26712 (or 26703 counting only the distinct ones).

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

The square root of 21621330 is about 4649.8741918465. The cubic root of 21621330 is about 278.5869712376.

Adding to 21621330 its reverse (3312612), we get a palindrome (24933942).

The spelling of 21621330 in words is "twenty-one million, six hundred twenty-one thousand, three hundred thirty".