21426251 has 16 divisors (see below), whose sum is σ = 26815488. Its totient is φ = 16632000.

The previous prime is 21426247. The next prime is 21426253. The reversal of 21426251 is 15262412.

It is a happy number.

It is not a de Polignac number, because 21426251 - 2² = 21426247 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21426253) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 35351 + ... + 35951.

It is an arithmetic number, because the mean of its divisors is an integer number (1675968).

Almost surely, 2^21426251 is an apocalyptic number.

21426251 is a deficient number, since it is larger than the sum of its proper divisors (5389237).

21426251 is a wasteful number, since it uses less digits than its factorization.

21426251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1082.

The product of its digits is 960, while the sum is 23.

The square root of 21426251 is about 4628.8498571459. The cubic root of 21426251 is about 277.7465860028.

Adding to 21426251 its reverse (15262412), we get a palindrome (36688663).

The spelling of 21426251 in words is "twenty-one million, four hundred twenty-six thousand, two hundred fifty-one".