21621245 has 8 divisors (see below), whose sum is σ = 26198016. Its totient is φ = 17128656.

The previous prime is 21621239. The next prime is 21621277. The reversal of 21621245 is 54212612.

It is a happy number.

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 21621245 - 2⁶ = 21621181 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21621245.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20477 + ... + 21506.

It is an arithmetic number, because the mean of its divisors is an integer number (3274752).

Almost surely, 2^21621245 is an apocalyptic number.

It is an amenable number.

21621245 is a deficient number, since it is larger than the sum of its proper divisors (4576771).

21621245 is a wasteful number, since it uses less digits than its factorization.

21621245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42091.

The product of its digits is 960, while the sum is 23.

The square root of 21621245 is about 4649.8650518053. The cubic root of 21621245 is about 278.5866061672.

Adding to 21621245 its reverse (54212612), we get a palindrome (75833857).

The spelling of 21621245 in words is "twenty-one million, six hundred twenty-one thousand, two hundred forty-five".