21399554 has 16 divisors (see below), whose sum is σ = 35103456. Its totient is φ = 9703200.

The previous prime is 21399551. The next prime is 21399559. The reversal of 21399554 is 45599312.

It is a super-2 number, since 2×21399554² = 915881822797832, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21399551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10529 + ... + 12395.

It is an arithmetic number, because the mean of its divisors is an integer number (2193966).

Almost surely, 2^21399554 is an apocalyptic number.

21399554 is a deficient number, since it is larger than the sum of its proper divisors (13703902).

21399554 is a wasteful number, since it uses less digits than its factorization.

21399554 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2401.

The product of its digits is 48600, while the sum is 38.

The square root of 21399554 is about 4625.9651965833. The cubic root of 21399554 is about 277.6311811127.

The spelling of 21399554 in words is "twenty-one million, three hundred ninety-nine thousand, five hundred fifty-four".