21156921998 has 16 divisors (see below), whose sum is σ = 31811063904. Its totient is φ = 10553262720.

The previous prime is 21156921983. The next prime is 21156922013. The reversal of 21156921998 is 89912965112.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21156921983) and next prime (21156922013).

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, 1703186 + ... + 1715562.

It is an arithmetic number, because the mean of its divisors is an integer number (1988191494).

Almost surely, 2^21156921998 is an apocalyptic number.

21156921998 is a deficient number, since it is larger than the sum of its proper divisors (10654141906).

21156921998 is a wasteful number, since it uses less digits than its factorization.

21156921998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14347.

The product of its digits is 699840, while the sum is 53.

The spelling of 21156921998 in words is "twenty-one billion, one hundred fifty-six million, nine hundred twenty-one thousand, nine hundred ninety-eight".