21125389 has 2 divisors, whose sum is σ = 21125390. Its totient is φ = 21125388.

The previous prime is 21125381. The next prime is 21125393. The reversal of 21125389 is 98352112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17388900 + 3736489 = 4170^2 + 1933^2 .

It is a cyclic number.

It is not a de Polignac number, because 21125389 - 2³ = 21125381 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21125389.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21125381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10562694 + 10562695.

It is an arithmetic number, because the mean of its divisors is an integer number (10562695).

Almost surely, 2^21125389 is an apocalyptic number.

It is an amenable number.

21125389 is a deficient number, since it is larger than the sum of its proper divisors (1).

21125389 is an equidigital number, since it uses as much as digits as its factorization.

21125389 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 31.

The square root of 21125389 is about 4596.2363951390. The cubic root of 21125389 is about 276.4404374731.

It can be divided in two parts, 211 and 25389, that added together give a square (25600 = 160²).

The spelling of 21125389 in words is "twenty-one million, one hundred twenty-five thousand, three hundred eighty-nine".