21151008 has 54 divisors (see below), whose sum is σ = 60370947. Its totient is φ = 7024320.

The previous prime is 21150991. The next prime is 21151027. The reversal of 21151008 is 80015112.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in only one way, i.e., 10575504 + 10575504 = 3252^2 + 3252^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=3252.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 77913 + ... + 78183.

Almost surely, 2^21151008 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21151008

21151008 is an abundant number, since it is smaller than the sum of its proper divisors (39219939).

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

21151008 is an equidigital number, since it uses as much as digits as its factorization.

21151008 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 558 (or 276 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 18.

The square root of 21151008 is about 4599.0225048373. The cubic root of 21151008 is about 276.5521398207.

Multiplying 21151008 by its sum of digits (18), we get a square (380718144 = 19512²).

21151008 divided by its sum of digits (18) gives a square (1175056 = 1084²).

The spelling of 21151008 in words is "twenty-one million, one hundred fifty-one thousand, eight".