21761953 has 4 divisors (see below), whose sum is σ = 21771520. Its totient is φ = 21752388.

The previous prime is 21761947. The next prime is 21761983. The reversal of 21761953 is 35916712.

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 a de Polignac number, because none of the positive numbers 2^k-21761953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21761983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 808 + ... + 6646.

It is an arithmetic number, because the mean of its divisors is an integer number (5442880).

Almost surely, 2^21761953 is an apocalyptic number.

It is an amenable number.

21761953 is a deficient number, since it is larger than the sum of its proper divisors (9567).

21761953 is an equidigital number, since it uses as much as digits as its factorization.

21761953 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9566.

The product of its digits is 11340, while the sum is 34.

The square root of 21761953 is about 4664.9708466399. The cubic root of 21761953 is about 279.1896339709.

The spelling of 21761953 in words is "twenty-one million, seven hundred sixty-one thousand, nine hundred fifty-three".