21248621 has 4 divisors (see below), whose sum is σ = 21539772. Its totient is φ = 20957472.

The previous prime is 21248599. The next prime is 21248639. The reversal of 21248621 is 12684212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15319396 + 5929225 = 3914^2 + 2435^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21248621 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 (21248641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 145466 + ... + 145611.

It is an arithmetic number, because the mean of its divisors is an integer number (5384943).

Almost surely, 2^21248621 is an apocalyptic number.

It is an amenable number.

21248621 is a deficient number, since it is larger than the sum of its proper divisors (291151).

21248621 is an equidigital number, since it uses as much as digits as its factorization.

21248621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291150.

The product of its digits is 1536, while the sum is 26.

The square root of 21248621 is about 4609.6226526691. The cubic root of 21248621 is about 276.9769211875.

The spelling of 21248621 in words is "twenty-one million, two hundred forty-eight thousand, six hundred twenty-one".