21154789 has 2 divisors, whose sum is σ = 21154790. Its totient is φ = 21154788.

The previous prime is 21154759. The next prime is 21154799. The reversal of 21154789 is 98745112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17222500 + 3932289 = 4150^2 + 1983^2 .

It is a cyclic number.

It is not a de Polignac number, because 21154789 - 2¹⁹ = 20630501 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21154709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577394 + 10577395.

It is an arithmetic number, because the mean of its divisors is an integer number (10577395).

Almost surely, 2^21154789 is an apocalyptic number.

It is an amenable number.

21154789 is a deficient number, since it is larger than the sum of its proper divisors (1).

21154789 is an equidigital number, since it uses as much as digits as its factorization.

21154789 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20160, while the sum is 37.

The square root of 21154789 is about 4599.4335520801. The cubic root of 21154789 is about 276.5686178586.

The spelling of 21154789 in words is "twenty-one million, one hundred fifty-four thousand, seven hundred eighty-nine".