21865049 has 4 divisors (see below), whose sum is σ = 21890064. Its totient is φ = 21840036.

The previous prime is 21865037. The next prime is 21865057. The reversal of 21865049 is 94056812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21865049 - 2¹⁶ = 21799513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21865099) 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, 11147 + ... + 12960.

It is an arithmetic number, because the mean of its divisors is an integer number (5472516).

Almost surely, 2^21865049 is an apocalyptic number.

It is an amenable number.

21865049 is a deficient number, since it is larger than the sum of its proper divisors (25015).

21865049 is an equidigital number, since it uses as much as digits as its factorization.

21865049 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25014.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 21865049 is about 4676.0078058104. The cubic root of 21865049 is about 279.6298211886.

The spelling of 21865049 in words is "twenty-one million, eight hundred sixty-five thousand, forty-nine".