21051953 has 4 divisors (see below), whose sum is σ = 22671348. Its totient is φ = 19432560.

The previous prime is 21051949. The next prime is 21051977. The reversal of 21051953 is 35915012.

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 3268864 + 17783089 = 1808^2 + 4217^2 .

It is a cyclic number.

It is not a de Polignac number, because 21051953 - 2² = 21051949 is a prime.

It is a super-2 number, since 2×21051953² = 886369450228418, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21051913) 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, 809678 + ... + 809703.

It is an arithmetic number, because the mean of its divisors is an integer number (5667837).

Almost surely, 2^21051953 is an apocalyptic number.

It is an amenable number.

21051953 is a deficient number, since it is larger than the sum of its proper divisors (1619395).

21051953 is a wasteful number, since it uses less digits than its factorization.

21051953 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1619394.

The product of its (nonzero) digits is 1350, while the sum is 26.

The square root of 21051953 is about 4588.2407303889. The cubic root of 21051953 is about 276.1197451764.

Adding to 21051953 its reverse (35915012), we get a palindrome (56966965).

The spelling of 21051953 in words is "twenty-one million, fifty-one thousand, nine hundred fifty-three".