21966815 has 16 divisors (see below), whose sum is σ = 28501536. Its totient is φ = 16156800.

The previous prime is 21966811. The next prime is 21966823. The reversal of 21966815 is 51866912.

It is not a de Polignac number, because 21966815 - 2² = 21966811 is a prime.

It is a super-2 number, since 2×21966815² = 965081922488450, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21966811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21005 + ... + 22025.

It is an arithmetic number, because the mean of its divisors is an integer number (1781346).

Almost surely, 2^21966815 is an apocalyptic number.

21966815 is a deficient number, since it is larger than the sum of its proper divisors (6534721).

21966815 is a wasteful number, since it uses less digits than its factorization.

21966815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1370.

The product of its digits is 25920, while the sum is 38.

The square root of 21966815 is about 4686.8768919185. The cubic root of 21966815 is about 280.0629747809.

The spelling of 21966815 in words is "twenty-one million, nine hundred sixty-six thousand, eight hundred fifteen".