21628515 has 16 divisors (see below), whose sum is σ = 35193600. Its totient is φ = 11339232.

The previous prime is 21628501. The next prime is 21628553. The reversal of 21628515 is 51582612.

It is not a de Polignac number, because 21628515 - 2¹³ = 21620323 is a prime.

It is a super-2 number, since 2×21628515² = 935585322210450, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11335 + ... + 13104.

It is an arithmetic number, because the mean of its divisors is an integer number (2199600).

Almost surely, 2^21628515 is an apocalyptic number.

21628515 is a deficient number, since it is larger than the sum of its proper divisors (13565085).

21628515 is a wasteful number, since it uses less digits than its factorization.

21628515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24506.

The product of its digits is 4800, while the sum is 30.

The square root of 21628515 is about 4650.6467292195. The cubic root of 21628515 is about 278.6178269668.

The spelling of 21628515 in words is "twenty-one million, six hundred twenty-eight thousand, five hundred fifteen".