21151853 has 4 divisors (see below), whose sum is σ = 21161088. Its totient is φ = 21142620.

The previous prime is 21151813. The next prime is 21151873. The reversal of 21151853 is 35815112.

It is a happy number.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21151853 - 2¹⁸ = 20889709 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21151813) 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, 1700 + ... + 6722.

It is an arithmetic number, because the mean of its divisors is an integer number (5290272).

Almost surely, 2^21151853 is an apocalyptic number.

It is an amenable number.

21151853 is a deficient number, since it is larger than the sum of its proper divisors (9235).

21151853 is an equidigital number, since it uses as much as digits as its factorization.

21151853 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9234.

The product of its digits is 1200, while the sum is 26.

The square root of 21151853 is about 4599.1143712676. The cubic root of 21151853 is about 276.5558225994. Note that the first 3 decimals are identical.

Adding to 21151853 its reverse (35815112), we get a palindrome (56966965).

The spelling of 21151853 in words is "twenty-one million, one hundred fifty-one thousand, eight hundred fifty-three".