21553705 has 8 divisors (see below), whose sum is σ = 27385992. Its totient is φ = 16228608.

The previous prime is 21553643. The next prime is 21553717. The reversal of 21553705 is 50735512.

It can be written as a sum of positive squares in 4 ways, for example, as 4214809 + 17338896 = 2053^2 + 4164^2 .

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

It is not a de Polignac number, because 21553705 - 2¹¹ = 21551657 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 126702 + ... + 126871.

It is an arithmetic number, because the mean of its divisors is an integer number (3423249).

Almost surely, 2^21553705 is an apocalyptic number.

It is an amenable number.

21553705 is a deficient number, since it is larger than the sum of its proper divisors (5832287).

21553705 is a wasteful number, since it uses less digits than its factorization.

21553705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 253595.

The product of its (nonzero) digits is 5250, while the sum is 28.

The square root of 21553705 is about 4642.5967948983. The cubic root of 21553705 is about 278.2962225572.

The spelling of 21553705 in words is "twenty-one million, five hundred fifty-three thousand, seven hundred five".