21535144 has 8 divisors (see below), whose sum is σ = 40378410. Its totient is φ = 10767568.

The previous prime is 21535123. The next prime is 21535169. The reversal of 21535144 is 44153512.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 13972644 + 7562500 = 3738^2 + 2750^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1345939 + ... + 1345954.

Almost surely, 2^21535144 is an apocalyptic number.

It is an amenable number.

21535144 is a deficient number, since it is larger than the sum of its proper divisors (18843266).

21535144 is a wasteful number, since it uses less digits than its factorization.

21535144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2691899 (or 2691895 counting only the distinct ones).

The product of its digits is 2400, while the sum is 25.

The square root of 21535144 is about 4640.5973753387. The cubic root of 21535144 is about 278.2163145686.

Adding to 21535144 its reverse (44153512), we get a palindrome (65688656).

The spelling of 21535144 in words is "twenty-one million, five hundred thirty-five thousand, one hundred forty-four".