21121646 has 48 divisors (see below), whose sum is σ = 40506480. Its totient is φ = 8184960.

The previous prime is 21121631. The next prime is 21121649. The reversal of 21121646 is 64612112.

It is a super-2 number, since 2×21121646² = 892247859498632, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121649) 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 23 ways as a sum of consecutive naturals, for example, 75026 + ... + 75306.

It is an arithmetic number, because the mean of its divisors is an integer number (843885).

Almost surely, 2^21121646 is an apocalyptic number.

21121646 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21121646 is a deficient number, since it is larger than the sum of its proper divisors (19384834).

21121646 is a wasteful number, since it uses less digits than its factorization.

21121646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 369 (or 362 counting only the distinct ones).

The product of its digits is 576, while the sum is 23.

The square root of 21121646 is about 4595.8291961299. The cubic root of 21121646 is about 276.4241099209.

Adding to 21121646 its reverse (64612112), we get a palindrome (85733758).

The spelling of 21121646 in words is "twenty-one million, one hundred twenty-one thousand, six hundred forty-six".