21405607 has 2 divisors, whose sum is σ = 21405608. Its totient is φ = 21405606.

The previous prime is 21405589. The next prime is 21405611. The reversal of 21405607 is 70650412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21405607 - 2¹¹ = 21403559 is a prime.

It is a super-2 number, since 2×21405607² = 916400022076898, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21405667) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702803 + 10702804.

It is an arithmetic number, because the mean of its divisors is an integer number (10702804).

Almost surely, 2^21405607 is an apocalyptic number.

21405607 is a deficient number, since it is larger than the sum of its proper divisors (1).

21405607 is an equidigital number, since it uses as much as digits as its factorization.

21405607 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 21405607 is about 4626.6193921696. The cubic root of 21405607 is about 277.6573552270.

The spelling of 21405607 in words is "twenty-one million, four hundred five thousand, six hundred seven".