21556457 has 12 divisors (see below), whose sum is σ = 23486220. Its totient is φ = 19775808.

The previous prime is 21556441. The next prime is 21556477. The reversal of 21556457 is 75465512.

It can be written as a sum of positive squares in 6 ways, for example, as 2859481 + 18696976 = 1691^2 + 4324^2 .

It is not a de Polignac number, because 21556457 - 2⁴ = 21556441 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21556477) 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 11 ways as a sum of consecutive naturals, for example, 38423 + ... + 38979.

It is an arithmetic number, because the mean of its divisors is an integer number (1957185).

Almost surely, 2^21556457 is an apocalyptic number.

It is an amenable number.

21556457 is a deficient number, since it is larger than the sum of its proper divisors (1929763).

21556457 is a wasteful number, since it uses less digits than its factorization.

21556457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 812 (or 799 counting only the distinct ones).

The product of its digits is 42000, while the sum is 35.

The square root of 21556457 is about 4642.8931712888. The cubic root of 21556457 is about 278.3080664392.

The spelling of 21556457 in words is "twenty-one million, five hundred fifty-six thousand, four hundred fifty-seven".