21859961 has 4 divisors (see below), whose sum is σ = 21871524. Its totient is φ = 21848400.

The previous prime is 21859949. The next prime is 21859973. The reversal of 21859961 is 16995812.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (21859949) and next prime (21859973).

It can be written as a sum of positive squares in 2 ways, for example, as 4687225 + 17172736 = 2165^2 + 4144^2 .

It is a cyclic number.

It is not a de Polignac number, because 21859961 - 2⁶ = 21859897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21859921) 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, 2210 + ... + 6971.

It is an arithmetic number, because the mean of its divisors is an integer number (5467881).

Almost surely, 2^21859961 is an apocalyptic number.

It is an amenable number.

21859961 is a deficient number, since it is larger than the sum of its proper divisors (11563).

21859961 is an equidigital number, since it uses as much as digits as its factorization.

21859961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11562.

The product of its digits is 38880, while the sum is 41.

The square root of 21859961 is about 4675.4637203169. The cubic root of 21859961 is about 279.6081295396.

The spelling of 21859961 in words is "twenty-one million, eight hundred fifty-nine thousand, nine hundred sixty-one".