21401515 has 8 divisors (see below), whose sum is σ = 25785648. Its totient is φ = 17052000.

The previous prime is 21401473. The next prime is 21401531. The reversal of 21401515 is 51510412.

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

It is a de Polignac number, because none of the positive numbers 2^k-21401515 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21401492 and 21401501.

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, 7272 + ... + 9781.

It is an arithmetic number, because the mean of its divisors is an integer number (3223206).

Almost surely, 2^21401515 is an apocalyptic number.

21401515 is a deficient number, since it is larger than the sum of its proper divisors (4384133).

21401515 is a wasteful number, since it uses less digits than its factorization.

21401515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17309.

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

The square root of 21401515 is about 4626.1771474945. The cubic root of 21401515 is about 277.6396613224.

Adding to 21401515 its reverse (51510412), we get a palindrome (72911927).

It can be divided in two parts, 2140 and 1515, that added together give a triangular number (3655 = T₈₅).

The spelling of 21401515 in words is "twenty-one million, four hundred one thousand, five hundred fifteen".