21543572 has 6 divisors (see below), whose sum is σ = 37701258. Its totient is φ = 10771784.

The previous prime is 21543569. The next prime is 21543589. The reversal of 21543572 is 27534512.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21492496 + 51076 = 4636^2 + 226^2 .

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 2692943 + ... + 2692950.

It is an arithmetic number, because the mean of its divisors is an integer number (6283543).

Almost surely, 2^21543572 is an apocalyptic number.

It is an amenable number.

21543572 is a deficient number, since it is larger than the sum of its proper divisors (16157686).

21543572 is a wasteful number, since it uses less digits than its factorization.

21543572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5385897 (or 5385895 counting only the distinct ones).

The product of its digits is 8400, while the sum is 29.

The square root of 21543572 is about 4641.5053592558. The cubic root of 21543572 is about 278.2526041066.

The spelling of 21543572 in words is "twenty-one million, five hundred forty-three thousand, five hundred seventy-two".