21742901 has 4 divisors (see below), whose sum is σ = 22099404. Its totient is φ = 21386400.

The previous prime is 21742829. The next prime is 21742913. The reversal of 21742901 is 10924712.

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 11566801 + 10176100 = 3401^2 + 3190^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21742901 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 (21742961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 178160 + ... + 178281.

It is an arithmetic number, because the mean of its divisors is an integer number (5524851).

Almost surely, 2^21742901 is an apocalyptic number.

It is an amenable number.

21742901 is a deficient number, since it is larger than the sum of its proper divisors (356503).

21742901 is an equidigital number, since it uses as much as digits as its factorization.

21742901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 356502.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 21742901 is about 4662.9283717424. The cubic root of 21742901 is about 279.1081358641.

The spelling of 21742901 in words is "twenty-one million, seven hundred forty-two thousand, nine hundred one".