21471557 has 4 divisors (see below), whose sum is σ = 21792096. Its totient is φ = 21151020.

The previous prime is 21471533. The next prime is 21471589. The reversal of 21471557 is 75517412.

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 21471557 - 2⁸ = 21471301 is a prime.

It is a super-2 number, since 2×21471557² = 922055520008498, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21471157) 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, 160169 + ... + 160302.

It is an arithmetic number, because the mean of its divisors is an integer number (5448024).

Almost surely, 2^21471557 is an apocalyptic number.

It is an amenable number.

21471557 is a deficient number, since it is larger than the sum of its proper divisors (320539).

21471557 is an equidigital number, since it uses as much as digits as its factorization.

21471557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320538.

The product of its digits is 9800, while the sum is 32.

The square root of 21471557 is about 4633.7411451224. The cubic root of 21471557 is about 277.9422140645.

Adding to 21471557 its reverse (75517412), we get a palindrome (96988969).

The spelling of 21471557 in words is "twenty-one million, four hundred seventy-one thousand, five hundred fifty-seven".