21700817 has 4 divisors (see below), whose sum is σ = 21711780. Its totient is φ = 21689856.

The previous prime is 21700771. The next prime is 21700829. The reversal of 21700817 is 71800712.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 14432401 + 7268416 = 3799^2 + 2696^2 .

It is a cyclic number.

It is not a de Polignac number, because 21700817 - 2⁸ = 21700561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21700117) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1592 + ... + 6777.

It is an arithmetic number, because the mean of its divisors is an integer number (5427945).

Almost surely, 2^21700817 is an apocalyptic number.

It is an amenable number.

21700817 is a deficient number, since it is larger than the sum of its proper divisors (10963).

21700817 is an equidigital number, since it uses as much as digits as its factorization.

21700817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10962.

The product of its (nonzero) digits is 784, while the sum is 26.

The square root of 21700817 is about 4658.4135711635. The cubic root of 21700817 is about 278.9279456619.

The spelling of 21700817 in words is "twenty-one million, seven hundred thousand, eight hundred seventeen".