21621016 has 16 divisors (see below), whose sum is σ = 40602240. Its totient is φ = 10793760.

The previous prime is 21621013. The next prime is 21621029. The reversal of 21621016 is 61012612.

It is a junction number, because it is equal to n+sod(n) for n = 21620984 and 21621002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21621013) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4681 + ... + 8071.

It is an arithmetic number, because the mean of its divisors is an integer number (2537640).

Almost surely, 2^21621016 is an apocalyptic number.

It is an amenable number.

21621016 is a deficient number, since it is larger than the sum of its proper divisors (18981224).

21621016 is a wasteful number, since it uses less digits than its factorization.

21621016 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4194 (or 4190 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 21621016 is about 4649.8404273695. The cubic root of 21621016 is about 278.5856226198.

Adding to 21621016 its reverse (61012612), we get a palindrome (82633628).

The spelling of 21621016 in words is "twenty-one million, six hundred twenty-one thousand, sixteen".