21154015 has 4 divisors (see below), whose sum is σ = 25384824. Its totient is φ = 16923208.

The previous prime is 21153971. The next prime is 21154019. The reversal of 21154015 is 51045112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21154015 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21153983 and 21154001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21154019) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 2115397 + ... + 2115406.

It is an arithmetic number, because the mean of its divisors is an integer number (6346206).

Almost surely, 2^21154015 is an apocalyptic number.

21154015 is a deficient number, since it is larger than the sum of its proper divisors (4230809).

21154015 is an equidigital number, since it uses as much as digits as its factorization.

21154015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4230808.

The product of its (nonzero) digits is 200, while the sum is 19.

The square root of 21154015 is about 4599.3494105145. The cubic root of 21154015 is about 276.5652448364.

Adding to 21154015 its reverse (51045112), we get a palindrome (72199127).

The spelling of 21154015 in words is "twenty-one million, one hundred fifty-four thousand, fifteen".