21209450 has 24 divisors (see below), whose sum is σ = 41167008. Its totient is φ = 8114480.

The previous prime is 21209443. The next prime is 21209459. The reversal of 21209450 is 5490212.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is not an unprimeable number, because it can be changed into a prime (21209459) 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 in 11 ways as a sum of consecutive naturals, for example, 8072 + ... + 10371.

It is an arithmetic number, because the mean of its divisors is an integer number (1715292).

Almost surely, 2^21209450 is an apocalyptic number.

21209450 is a deficient number, since it is larger than the sum of its proper divisors (19957558).

21209450 is a wasteful number, since it uses less digits than its factorization.

21209450 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18478 (or 18473 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21209450 is about 4605.3718633787. The cubic root of 21209450 is about 276.8066177959.

Adding to 21209450 its reverse (5490212), we get a palindrome (26699662).

It can be divided in two parts, 2 and 1209450, that multiplied together give a triangular number (2418900 = T₂₁₉₉).

The spelling of 21209450 in words is "twenty-one million, two hundred nine thousand, four hundred fifty".