21621907 has 8 divisors (see below), whose sum is σ = 22748400. Its totient is φ = 20520864.

The previous prime is 21621881. The next prime is 21621923. The reversal of 21621907 is 70912612.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21621907 - 2⁷ = 21621779 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21621937) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4608 + ... + 8029.

It is an arithmetic number, because the mean of its divisors is an integer number (2843550).

Almost surely, 2^21621907 is an apocalyptic number.

21621907 is a deficient number, since it is larger than the sum of its proper divisors (1126493).

21621907 is a wasteful number, since it uses less digits than its factorization.

21621907 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12725.

The product of its (nonzero) digits is 1512, while the sum is 28.

The square root of 21621907 is about 4649.9362361220. The cubic root of 21621907 is about 278.5894493962.

The spelling of 21621907 in words is "twenty-one million, six hundred twenty-one thousand, nine hundred seven".