21445621 has 8 divisors (see below), whose sum is σ = 21859200. Its totient is φ = 21035280.

The previous prime is 21445609. The next prime is 21445643. The reversal of 21445621 is 12654412.

It is a happy number.

21445621 is nontrivially palindromic in base 15.

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

It is a cyclic number.

It is not a de Polignac number, because 21445621 - 2⁷ = 21445493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21445651) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15600 + ... + 16918.

It is an arithmetic number, because the mean of its divisors is an integer number (2732400).

Almost surely, 2^21445621 is an apocalyptic number.

It is an amenable number.

21445621 is a deficient number, since it is larger than the sum of its proper divisors (413579).

21445621 is a wasteful number, since it uses less digits than its factorization.

21445621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1619.

The product of its digits is 1920, while the sum is 25.

The square root of 21445621 is about 4630.9416968906. The cubic root of 21445621 is about 277.8302579895.

The spelling of 21445621 in words is "twenty-one million, four hundred forty-five thousand, six hundred twenty-one".