21556745 has 8 divisors (see below), whose sum is σ = 29563584. Its totient is φ = 14781744.

The previous prime is 21556739. The next prime is 21556753. The reversal of 21556745 is 54765512.

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 21556745 - 2⁸ = 21556489 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (35), and also a Moran number because the ratio is a prime number: 615907 = 21556745 / (2 + 1 + 5 + 5 + 6 + 7 + 4 + 5).

It is a Duffinian number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 307919 + ... + 307988.

It is an arithmetic number, because the mean of its divisors is an integer number (3695448).

Almost surely, 2^21556745 is an apocalyptic number.

It is an amenable number.

21556745 is a deficient number, since it is larger than the sum of its proper divisors (8006839).

21556745 is an equidigital number, since it uses as much as digits as its factorization.

21556745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 615919.

The product of its digits is 42000, while the sum is 35.

The square root of 21556745 is about 4642.9241863291. The cubic root of 21556745 is about 278.3093058569.

The spelling of 21556745 in words is "twenty-one million, five hundred fifty-six thousand, seven hundred forty-five".