21211653 has 4 divisors (see below), whose sum is σ = 28282208. Its totient is φ = 14141100.

The previous prime is 21211643. The next prime is 21211709. The reversal of 21211653 is 35611212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21211653 - 2²² = 17017349 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211613) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3535273 + ... + 3535278.

It is an arithmetic number, because the mean of its divisors is an integer number (7070552).

Almost surely, 2^21211653 is an apocalyptic number.

It is an amenable number.

21211653 is a deficient number, since it is larger than the sum of its proper divisors (7070555).

21211653 is an equidigital number, since it uses as much as digits as its factorization.

21211653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7070554.

The product of its digits is 360, while the sum is 21.

The square root of 21211653 is about 4605.6110343797. The cubic root of 21211653 is about 276.8162013207.

Adding to 21211653 its reverse (35611212), we get a palindrome (56822865).

The spelling of 21211653 in words is "twenty-one million, two hundred eleven thousand, six hundred fifty-three".