21001457 has 4 divisors (see below), whose sum is σ = 21046896. Its totient is φ = 20956020.

The previous prime is 21001447. The next prime is 21001469. The reversal of 21001457 is 75410012.

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 a cyclic number.

It is not a de Polignac number, because 21001457 - 2¹⁰ = 21000433 is a prime.

It is a super-2 number, since 2×21001457² = 882122392245698, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21001417) 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, 22019 + ... + 22952.

It is an arithmetic number, because the mean of its divisors is an integer number (5261724).

Almost surely, 2^21001457 is an apocalyptic number.

It is an amenable number.

21001457 is a deficient number, since it is larger than the sum of its proper divisors (45439).

21001457 is an equidigital number, since it uses as much as digits as its factorization.

21001457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45438.

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 21001457 is about 4582.7346639316. The cubic root of 21001457 is about 275.8987980501.

Adding to 21001457 its reverse (75410012), we get a palindrome (96411469).

The spelling of 21001457 in words is "twenty-one million, one thousand, four hundred fifty-seven".