21855739 has 4 divisors (see below), whose sum is σ = 22364056. Its totient is φ = 21347424.

The previous prime is 21855737. The next prime is 21855781. The reversal of 21855739 is 93755812.

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 21855739 - 2¹ = 21855737 is a prime.

It is a super-2 number, since 2×21855739² = 955346654472242, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21855737) 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, 254094 + ... + 254179.

It is an arithmetic number, because the mean of its divisors is an integer number (5591014).

Almost surely, 2^21855739 is an apocalyptic number.

21855739 is a deficient number, since it is larger than the sum of its proper divisors (508317).

21855739 is an equidigital number, since it uses as much as digits as its factorization.

21855739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 508316.

The product of its digits is 75600, while the sum is 40.

The square root of 21855739 is about 4675.0121924975. The cubic root of 21855739 is about 279.5901273493.

The spelling of 21855739 in words is "twenty-one million, eight hundred fifty-five thousand, seven hundred thirty-nine".