21542644 has 24 divisors (see below), whose sum is σ = 39511808. Its totient is φ = 10264320.

The previous prime is 21542639. The next prime is 21542663. The reversal of 21542644 is 44624512.

It is a congruent number.

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 in 7 ways as a sum of consecutive naturals, for example, 7012 + ... + 9604.

Almost surely, 2^21542644 is an apocalyptic number.

It is an amenable number.

21542644 is a deficient number, since it is larger than the sum of its proper divisors (17969164).

21542644 is a wasteful number, since it uses less digits than its factorization.

21542644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2695 (or 2693 counting only the distinct ones).

The product of its digits is 7680, while the sum is 28.

The square root of 21542644 is about 4641.4053906118. The cubic root of 21542644 is about 278.2486087598.

It can be divided in two parts, 2 and 1542644, that added together give a triangular number (1542646 = T₁₇₅₆).

The spelling of 21542644 in words is "twenty-one million, five hundred forty-two thousand, six hundred forty-four".