21829861 has 2 divisors, whose sum is σ = 21829862. Its totient is φ = 21829860.

The previous prime is 21829817. The next prime is 21829897. The reversal of 21829861 is 16892812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15920100 + 5909761 = 3990^2 + 2431^2 .

It is a cyclic number.

It is not a de Polignac number, because 21829861 - 2⁹ = 21829349 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21829861.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21829361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10914930 + 10914931.

It is an arithmetic number, because the mean of its divisors is an integer number (10914931).

Almost surely, 2^21829861 is an apocalyptic number.

It is an amenable number.

21829861 is a deficient number, since it is larger than the sum of its proper divisors (1).

21829861 is an equidigital number, since it uses as much as digits as its factorization.

21829861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 37.

The square root of 21829861 is about 4672.2436794328. The cubic root of 21829861 is about 279.4797354321.

The spelling of 21829861 in words is "twenty-one million, eight hundred twenty-nine thousand, eight hundred sixty-one".