21457679 has 2 divisors, whose sum is σ = 21457680. Its totient is φ = 21457678.

The previous prime is 21457649. The next prime is 21457687. The reversal of 21457679 is 97675412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21457679 - 2¹² = 21453583 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21457649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10728839 + 10728840.

It is an arithmetic number, because the mean of its divisors is an integer number (10728840).

Almost surely, 2^21457679 is an apocalyptic number.

21457679 is a deficient number, since it is larger than the sum of its proper divisors (1).

21457679 is an equidigital number, since it uses as much as digits as its factorization.

21457679 is an evil number, because the sum of its binary digits is even.

The product of its digits is 105840, while the sum is 41.

The square root of 21457679 is about 4632.2434089758. The cubic root of 21457679 is about 277.8823191162.

The spelling of 21457679 in words is "twenty-one million, four hundred fifty-seven thousand, six hundred seventy-nine".