21501745 has 4 divisors (see below), whose sum is σ = 25802100. Its totient is φ = 17201392.

The previous prime is 21501737. The next prime is 21501811. The reversal of 21501745 is 54710512.

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

It can be written as a sum of positive squares in 2 ways, for example, as 3659569 + 17842176 = 1913^2 + 4224^2 .

It is a cyclic number.

It is not a de Polignac number, because 21501745 - 2³ = 21501737 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2150170 + ... + 2150179.

It is an arithmetic number, because the mean of its divisors is an integer number (6450525).

Almost surely, 2^21501745 is an apocalyptic number.

It is an amenable number.

21501745 is a deficient number, since it is larger than the sum of its proper divisors (4300355).

21501745 is an equidigital number, since it uses as much as digits as its factorization.

21501745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4300354.

The product of its (nonzero) digits is 1400, while the sum is 25.

The square root of 21501745 is about 4636.9974121192. The cubic root of 21501745 is about 278.0724109633.

The spelling of 21501745 in words is "twenty-one million, five hundred one thousand, seven hundred forty-five".