21097818 has 24 divisors (see below), whose sum is σ = 52242528. Its totient is φ = 6027912.

The previous prime is 21097759. The next prime is 21097823. The reversal of 21097818 is 81879012.

It is a super-2 number, since 2×21097818² = 890235848722248, which contains 22 as substring.

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 11 ways as a sum of consecutive naturals, for example, 83596 + ... + 83847.

It is an arithmetic number, because the mean of its divisors is an integer number (2176772).

Almost surely, 2^21097818 is an apocalyptic number.

21097818 is an abundant number, since it is smaller than the sum of its proper divisors (31144710).

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

21097818 is a wasteful number, since it uses less digits than its factorization.

21097818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167458 (or 167455 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 21097818 is about 4593.2361141139. The cubic root of 21097818 is about 276.3201232002.

The spelling of 21097818 in words is "twenty-one million, ninety-seven thousand, eight hundred eighteen".