21765505 has 16 divisors (see below), whose sum is σ = 26671680. Its totient is φ = 17048128.

The previous prime is 21765481. The next prime is 21765511. The reversal of 21765505 is 50556712.

It is a cyclic number.

It is not a de Polignac number, because 21765505 - 2¹⁷ = 21634433 is a prime.

It is a super-3 number, since 3×21765505³ (a number of 23 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 74139 + ... + 74431.

It is an arithmetic number, because the mean of its divisors is an integer number (1666980).

Almost surely, 2^21765505 is an apocalyptic number.

It is an amenable number.

21765505 is a deficient number, since it is larger than the sum of its proper divisors (4906175).

21765505 is a wasteful number, since it uses less digits than its factorization.

21765505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 560.

The product of its (nonzero) digits is 10500, while the sum is 31.

The square root of 21765505 is about 4665.3515408809. The cubic root of 21765505 is about 279.2048229819.

The spelling of 21765505 in words is "twenty-one million, seven hundred sixty-five thousand, five hundred five".