21400818 has 16 divisors (see below), whose sum is σ = 42850080. Its totient is φ = 7125536.

The previous prime is 21400801. The next prime is 21400823. The reversal of 21400818 is 81800412.

It is a super-2 number, since 2×21400818² = 915990022138248, which contains 22 as substring.

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, 6478 + ... + 9206.

It is an arithmetic number, because the mean of its divisors is an integer number (2678130).

Almost surely, 2^21400818 is an apocalyptic number.

21400818 is an abundant number, since it is smaller than the sum of its proper divisors (21449262).

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

21400818 is a wasteful number, since it uses less digits than its factorization.

21400818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4041.

The product of its (nonzero) digits is 512, while the sum is 24.

The square root of 21400818 is about 4626.1018147032. The cubic root of 21400818 is about 277.6366472532.

The spelling of 21400818 in words is "twenty-one million, four hundred thousand, eight hundred eighteen".