21053645 has 8 divisors (see below), whose sum is σ = 25307640. Its totient is φ = 16814080.

The previous prime is 21053639. The next prime is 21053651. The reversal of 21053645 is 54635012.

It is an interprime number because it is at equal distance from previous prime (21053639) and next prime (21053651).

It can be written as a sum of positive squares in 4 ways, for example, as 10569001 + 10484644 = 3251^2 + 3238^2 .

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

It is not a de Polignac number, because 21053645 - 2¹⁰ = 21052621 is a prime.

It is a super-3 number, since 3×21053645³ (a number of 23 digits) contains 333 as substring.

It is a Curzon number.

It is a congruent 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, 80 + ... + 6489.

It is an arithmetic number, because the mean of its divisors is an integer number (3163455).

Almost surely, 2^21053645 is an apocalyptic number.

It is an amenable number.

21053645 is a deficient number, since it is larger than the sum of its proper divisors (4253995).

21053645 is an equidigital number, since it uses as much as digits as its factorization.

21053645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7215.

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 21053645 is about 4588.4251110811. The cubic root of 21053645 is about 276.1271424646.

Adding to 21053645 its reverse (54635012), we get a palindrome (75688657).

The spelling of 21053645 in words is "twenty-one million, fifty-three thousand, six hundred forty-five".