21400389 has 24 divisors (see below), whose sum is σ = 32363520. Its totient is φ = 13975416.

The previous prime is 21400387. The next prime is 21400397. The reversal of 21400389 is 98300412.

It is not a de Polignac number, because 21400389 - 2¹ = 21400387 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21400381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 168444 + ... + 168570.

It is an arithmetic number, because the mean of its divisors is an integer number (1348480).

Almost surely, 2^21400389 is an apocalyptic number.

It is an amenable number.

21400389 is a deficient number, since it is larger than the sum of its proper divisors (10963131).

21400389 is an equidigital number, since it uses as much as digits as its factorization.

21400389 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 294 (or 209 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21400389 is about 4626.0554471385. The cubic root of 21400389 is about 277.6347920761.

The spelling of 21400389 in words is "twenty-one million, four hundred thousand, three hundred eighty-nine".