21578671 has 2 divisors, whose sum is σ = 21578672. Its totient is φ = 21578670.

The previous prime is 21578663. The next prime is 21578681. The reversal of 21578671 is 17687512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21578671 - 2³ = 21578663 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21578671.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21578651) 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 as a sum of consecutive naturals, namely, 10789335 + 10789336.

It is an arithmetic number, because the mean of its divisors is an integer number (10789336).

Almost surely, 2^21578671 is an apocalyptic number.

21578671 is a deficient number, since it is larger than the sum of its proper divisors (1).

21578671 is an equidigital number, since it uses as much as digits as its factorization.

21578671 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23520, while the sum is 37.

The square root of 21578671 is about 4645.2848136578. The cubic root of 21578671 is about 278.4036327462.

The spelling of 21578671 in words is "twenty-one million, five hundred seventy-eight thousand, six hundred seventy-one".