21512018 has 8 divisors (see below), whose sum is σ = 35201520. Its totient is φ = 9778180.

The previous prime is 21512017. The next prime is 21512027. The reversal of 21512018 is 81021512.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21512017) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 488888 + ... + 488931.

It is an arithmetic number, because the mean of its divisors is an integer number (4400190).

Almost surely, 2^21512018 is an apocalyptic number.

21512018 is a deficient number, since it is larger than the sum of its proper divisors (13689502).

21512018 is a wasteful number, since it uses less digits than its factorization.

21512018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 977832.

The product of its (nonzero) digits is 160, while the sum is 20.

The square root of 21512018 is about 4638.1050009675. The cubic root of 21512018 is about 278.1166892774.

The spelling of 21512018 in words is "twenty-one million, five hundred twelve thousand, eighteen".