21489945 has 32 divisors (see below), whose sum is σ = 35731584. Its totient is φ = 11020800.

The previous prime is 21489943. The next prime is 21489947. The reversal of 21489945 is 54998412.

21489945 = T₈₅ + T₈₆ + ... + T₅₀₅.

It is an interprime number because it is at equal distance from previous prime (21489943) and next prime (21489947).

It is not a de Polignac number, because 21489945 - 2¹ = 21489943 is a prime.

It is a super-2 number, since 2×21489945² = 923635472206050, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21489897 and 21489906.

It is not an unprimeable number, because it can be changed into a prime (21489943) 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 in 31 ways as a sum of consecutive naturals, for example, 50835 + ... + 51255.

It is an arithmetic number, because the mean of its divisors is an integer number (1116612).

Almost surely, 2^21489945 is an apocalyptic number.

It is an amenable number.

21489945 is a deficient number, since it is larger than the sum of its proper divisors (14241639).

21489945 is a wasteful number, since it uses less digits than its factorization.

21489945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 553.

The product of its digits is 103680, while the sum is 42.

The square root of 21489945 is about 4635.7248624136. The cubic root of 21489945 is about 278.0215336217.

The spelling of 21489945 in words is "twenty-one million, four hundred eighty-nine thousand, nine hundred forty-five".