84400021 has 2 divisors, whose sum is σ = 84400022. Its totient is φ = 84400020.

The previous prime is 84400003. The next prime is 84400037. The reversal of 84400021 is 12000448.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 83923921 + 476100 = 9161^2 + 690^2 .

It is a cyclic number.

It is not a de Polignac number, because 84400021 - 2⁵ = 84399989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (84400051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42200010 + 42200011.

It is an arithmetic number, because the mean of its divisors is an integer number (42200011).

Almost surely, 2^84400021 is an apocalyptic number.

It is an amenable number.

84400021 is a deficient number, since it is larger than the sum of its proper divisors (1).

84400021 is an equidigital number, since it uses as much as digits as its factorization.

84400021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 256, while the sum is 19.

The square root of 84400021 is about 9186.9484052105. The cubic root of 84400021 is about 438.6460116161.

Adding to 84400021 its reverse (12000448), we get a palindrome (96400469).

The spelling of 84400021 in words is "eighty-four million, four hundred thousand, twenty-one".