21489901 has 2 divisors, whose sum is σ = 21489902. Its totient is φ = 21489900.

The previous prime is 21489883. The next prime is 21489907. The reversal of 21489901 is 10998412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19802500 + 1687401 = 4450^2 + 1299^2 .

It is a cyclic number.

It is not a de Polignac number, because 21489901 - 2⁹ = 21489389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21489907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10744950 + 10744951.

It is an arithmetic number, because the mean of its divisors is an integer number (10744951).

Almost surely, 2^21489901 is an apocalyptic number.

It is an amenable number.

21489901 is a deficient number, since it is larger than the sum of its proper divisors (1).

21489901 is an equidigital number, since it uses as much as digits as its factorization.

21489901 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 21489901 is about 4635.7201166593. The cubic root of 21489901 is about 278.0213438748.

The spelling of 21489901 in words is "twenty-one million, four hundred eighty-nine thousand, nine hundred one".