21540621 has 16 divisors (see below), whose sum is σ = 29836800. Its totient is φ = 13812480.

The previous prime is 21540611. The next prime is 21540637. The reversal of 21540621 is 12604512.

It is a de Polignac number, because none of the positive numbers 2^k-21540621 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540611) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7780 + ... + 10178.

It is an arithmetic number, because the mean of its divisors is an integer number (1864800).

Almost surely, 2^21540621 is an apocalyptic number.

It is an amenable number.

21540621 is a deficient number, since it is larger than the sum of its proper divisors (8296179).

21540621 is a wasteful number, since it uses less digits than its factorization.

21540621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2516.

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21540621 is about 4641.1874558134. The cubic root of 21540621 is about 278.2398986782.

The spelling of 21540621 in words is "twenty-one million, five hundred forty thousand, six hundred twenty-one".