21501461 has 4 divisors (see below), whose sum is σ = 21513132. Its totient is φ = 21489792.

The previous prime is 21501451. The next prime is 21501479. The reversal of 21501461 is 16410512.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 4120900 + 17380561 = 2030^2 + 4169^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21501461 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21501401) 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, 2396 + ... + 6981.

It is an arithmetic number, because the mean of its divisors is an integer number (5378283).

Almost surely, 2^21501461 is an apocalyptic number.

It is an amenable number.

21501461 is a deficient number, since it is larger than the sum of its proper divisors (11671).

21501461 is an equidigital number, since it uses as much as digits as its factorization.

21501461 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11670.

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21501461 is about 4636.9667887532. The cubic root of 21501461 is about 278.0711866765.

Adding to 21501461 its reverse (16410512), we get a palindrome (37911973).

The spelling of 21501461 in words is "twenty-one million, five hundred one thousand, four hundred sixty-one".