21715541 has 2 divisors, whose sum is σ = 21715542. Its totient is φ = 21715540.

The previous prime is 21715489. The next prime is 21715621. The reversal of 21715541 is 14551712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21298225 + 417316 = 4615^2 + 646^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21715541 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21715541.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21715741) 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, 10857770 + 10857771.

It is an arithmetic number, because the mean of its divisors is an integer number (10857771).

Almost surely, 2^21715541 is an apocalyptic number.

It is an amenable number.

21715541 is a deficient number, since it is larger than the sum of its proper divisors (1).

21715541 is an equidigital number, since it uses as much as digits as its factorization.

21715541 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1400, while the sum is 26.

The square root of 21715541 is about 4659.9936695236. The cubic root of 21715541 is about 278.9910155849.

The spelling of 21715541 in words is "twenty-one million, seven hundred fifteen thousand, five hundred forty-one".