21354989 has 2 divisors, whose sum is σ = 21354990. Its totient is φ = 21354988.

The previous prime is 21354979. The next prime is 21355003. The reversal of 21354989 is 98945312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18576100 + 2778889 = 4310^2 + 1667^2 .

It is a cyclic number.

It is not a de Polignac number, because 21354989 - 2¹⁶ = 21289453 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21354959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10677494 + 10677495.

It is an arithmetic number, because the mean of its divisors is an integer number (10677495).

Almost surely, 2^21354989 is an apocalyptic number.

It is an amenable number.

21354989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21354989 is an equidigital number, since it uses as much as digits as its factorization.

21354989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 77760, while the sum is 41.

The square root of 21354989 is about 4621.1458535735. The cubic root of 21354989 is about 277.4383230078.

The spelling of 21354989 in words is "twenty-one million, three hundred fifty-four thousand, nine hundred eighty-nine".