21540646 has 4 divisors (see below), whose sum is σ = 32310972. Its totient is φ = 10770322.

The previous prime is 21540637. The next prime is 21540653. The reversal of 21540646 is 64604512.

It is a semiprime because it is the product of two primes.

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, 5385160 + ... + 5385163.

It is an arithmetic number, because the mean of its divisors is an integer number (8077743).

Almost surely, 2^21540646 is an apocalyptic number.

21540646 is a deficient number, since it is larger than the sum of its proper divisors (10770326).

21540646 is a wasteful number, since it uses less digits than its factorization.

21540646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10770325.

The product of its (nonzero) digits is 5760, while the sum is 28.

The square root of 21540646 is about 4641.1901490889. The cubic root of 21540646 is about 278.2400063197.

The spelling of 21540646 in words is "twenty-one million, five hundred forty thousand, six hundred forty-six".