21540729 has 8 divisors (see below), whose sum is σ = 32824000. Its totient is φ = 12308976.

The previous prime is 21540709. The next prime is 21540731. The reversal of 21540729 is 92704512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21540729 - 2⁸ = 21540473 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21540696 and 21540705.

It is not an unprimeable number, because it can be changed into a prime (21540709) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 512854 + ... + 512895.

It is an arithmetic number, because the mean of its divisors is an integer number (4103000).

Almost surely, 2^21540729 is an apocalyptic number.

It is an amenable number.

21540729 is a deficient number, since it is larger than the sum of its proper divisors (11283271).

21540729 is a wasteful number, since it uses less digits than its factorization.

21540729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1025759.

The product of its (nonzero) digits is 5040, while the sum is 30.

The square root of 21540729 is about 4641.1990907523. The cubic root of 21540729 is about 278.2403636890.

The spelling of 21540729 in words is "twenty-one million, five hundred forty thousand, seven hundred twenty-nine".