21461251 has 4 divisors (see below), whose sum is σ = 24527152. Its totient is φ = 18395352.

The previous prime is 21461249. The next prime is 21461287. The reversal of 21461251 is 15216412.

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

It is a cyclic number.

It is not a de Polignac number, because 21461251 - 2¹ = 21461249 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21461201) 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, 1532940 + ... + 1532953.

It is an arithmetic number, because the mean of its divisors is an integer number (6131788).

Almost surely, 2^21461251 is an apocalyptic number.

21461251 is a deficient number, since it is larger than the sum of its proper divisors (3065901).

21461251 is an equidigital number, since it uses as much as digits as its factorization.

21461251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3065900.

The product of its digits is 480, while the sum is 22.

The square root of 21461251 is about 4632.6289512544. The cubic root of 21461251 is about 277.8977376924.

Adding to 21461251 its reverse (15216412), we get a palindrome (36677663).

It can be divided in two parts, 21461 and 251, that added together give a palindrome (21712).

The spelling of 21461251 in words is "twenty-one million, four hundred sixty-one thousand, two hundred fifty-one".