21398811 has 16 divisors (see below), whose sum is σ = 33003264. Its totient is φ = 12079584.

The previous prime is 21398791. The next prime is 21398813. The reversal of 21398811 is 11889312.

It is not a de Polignac number, because 21398811 - 2⁵ = 21398779 is a prime.

It is a super-2 number, since 2×21398811² = 915818224427442, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21398813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4396 + ... + 7881.

It is an arithmetic number, because the mean of its divisors is an integer number (2062704).

Almost surely, 2^21398811 is an apocalyptic number.

21398811 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21398811 is a deficient number, since it is larger than the sum of its proper divisors (11604453).

21398811 is a wasteful number, since it uses less digits than its factorization.

21398811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12370.

The product of its digits is 3456, while the sum is 33.

The square root of 21398811 is about 4625.8848883214. The cubic root of 21398811 is about 277.6279679249.

The spelling of 21398811 in words is "twenty-one million, three hundred ninety-eight thousand, eight hundred eleven".