21534644 has 6 divisors (see below), whose sum is σ = 37685634. Its totient is φ = 10767320.

The previous prime is 21534577. The next prime is 21534659. The reversal of 21534644 is 44643512.

It can be written as a sum of positive squares in only one way, i.e., 19254544 + 2280100 = 4388^2 + 1510^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2691827 + ... + 2691834.

It is an arithmetic number, because the mean of its divisors is an integer number (6280939).

Almost surely, 2^21534644 is an apocalyptic number.

It is an amenable number.

21534644 is a deficient number, since it is larger than the sum of its proper divisors (16150990).

21534644 is a wasteful number, since it uses less digits than its factorization.

21534644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5383665 (or 5383663 counting only the distinct ones).

The product of its digits is 11520, while the sum is 29.

The square root of 21534644 is about 4640.5435026514. The cubic root of 21534644 is about 278.2141613559.

The spelling of 21534644 in words is "twenty-one million, five hundred thirty-four thousand, six hundred forty-four".