21403998 has 48 divisors (see below), whose sum is σ = 57822336. Its totient is φ = 5559120.

The previous prime is 21403979. The next prime is 21404017. The reversal of 21403998 is 89930412.

It is an interprime number because it is at equal distance from previous prime (21403979) and next prime (21404017).

It is a super-2 number, since 2×21403998² = 916262260768008, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6336 + ... + 9107.

It is an arithmetic number, because the mean of its divisors is an integer number (1204632).

Almost surely, 2^21403998 is an apocalyptic number.

21403998 is an abundant number, since it is smaller than the sum of its proper divisors (36418338).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21403998 is a wasteful number, since it uses less digits than its factorization.

21403998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15469 (or 15466 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 21403998 is about 4626.4455038399. The cubic root of 21403998 is about 277.6503981421.

The spelling of 21403998 in words is "twenty-one million, four hundred three thousand, nine hundred ninety-eight".