21989815 has 8 divisors (see below), whose sum is σ = 26473968. Its totient is φ = 17534400.

The previous prime is 21989797. The next prime is 21989833. The reversal of 21989815 is 51898912.

It is an interprime number because it is at equal distance from previous prime (21989797) and next prime (21989833).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21989815 - 2¹⁷ = 21858743 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5461 + ... + 8590.

It is an arithmetic number, because the mean of its divisors is an integer number (3309246).

Almost surely, 2^21989815 is an apocalyptic number.

21989815 is a deficient number, since it is larger than the sum of its proper divisors (4484153).

21989815 is a wasteful number, since it uses less digits than its factorization.

21989815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14369.

The product of its digits is 51840, while the sum is 43.

The square root of 21989815 is about 4689.3299094860. The cubic root of 21989815 is about 280.1606858295.

The spelling of 21989815 in words is "twenty-one million, nine hundred eighty-nine thousand, eight hundred fifteen".