21556099 has 4 divisors (see below), whose sum is σ = 21590064. Its totient is φ = 21522136.

The previous prime is 21556061. The next prime is 21556103. The reversal of 21556099 is 99065512.

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

It is a cyclic number.

It is not a de Polignac number, because 21556099 - 2¹³ = 21547907 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21556009) 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, 16012 + ... + 17305.

It is an arithmetic number, because the mean of its divisors is an integer number (5397516).

Almost surely, 2^21556099 is an apocalyptic number.

21556099 is a deficient number, since it is larger than the sum of its proper divisors (33965).

21556099 is an equidigital number, since it uses as much as digits as its factorization.

21556099 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33964.

The product of its (nonzero) digits is 24300, while the sum is 37.

The square root of 21556099 is about 4642.8546175817. The cubic root of 21556099 is about 278.3065257586.

The spelling of 21556099 in words is "twenty-one million, five hundred fifty-six thousand, ninety-nine".