21651244 has 6 divisors (see below), whose sum is σ = 37889684. Its totient is φ = 10825620.

The previous prime is 21651221. The next prime is 21651271. The reversal of 21651244 is 44215612.

It is a happy number.

It is a plaindrome in base 11.

It is an unprimeable number.

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, 2706402 + ... + 2706409.

Almost surely, 2^21651244 is an apocalyptic number.

It is an amenable number.

21651244 is a deficient number, since it is larger than the sum of its proper divisors (16238440).

21651244 is a wasteful number, since it uses less digits than its factorization.

21651244 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5412815 (or 5412813 counting only the distinct ones).

The product of its digits is 1920, while the sum is 25.

The square root of 21651244 is about 4653.0897261927. The cubic root of 21651244 is about 278.7153908784.

Adding to 21651244 its reverse (44215612), we get a palindrome (65866856).

The spelling of 21651244 in words is "twenty-one million, six hundred fifty-one thousand, two hundred forty-four".