21536989 has 2 divisors, whose sum is σ = 21536990. Its totient is φ = 21536988.

The previous prime is 21536953. The next prime is 21537001. The reversal of 21536989 is 98963512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19802500 + 1734489 = 4450^2 + 1317^2 .

It is a cyclic number.

It is not a de Polignac number, because 21536989 - 2¹⁹ = 21012701 is a prime.

It is a super-2 number, since 2×21536989² = 927683790372242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21536929) 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 as a sum of consecutive naturals, namely, 10768494 + 10768495.

It is an arithmetic number, because the mean of its divisors is an integer number (10768495).

Almost surely, 2^21536989 is an apocalyptic number.

It is an amenable number.

21536989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21536989 is an equidigital number, since it uses as much as digits as its factorization.

21536989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 116640, while the sum is 43.

The square root of 21536989 is about 4640.7961601432. The cubic root of 21536989 is about 278.2242596349.

The spelling of 21536989 in words is "twenty-one million, five hundred thirty-six thousand, nine hundred eighty-nine".