21436257 has 16 divisors (see below), whose sum is σ = 29098368. Its totient is φ = 14035200.

The previous prime is 21436243. The next prime is 21436271. The reversal of 21436257 is 75263412.

It is an interprime number because it is at equal distance from previous prime (21436243) and next prime (21436271).

It is not a de Polignac number, because 21436257 - 2⁴ = 21436241 is a prime.

It is a super-2 number, since 2×21436257² = 919026228340098, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21436757) 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, 53257 + ... + 53657.

It is an arithmetic number, because the mean of its divisors is an integer number (1818648).

Almost surely, 2^21436257 is an apocalyptic number.

It is an amenable number.

21436257 is a deficient number, since it is larger than the sum of its proper divisors (7662111).

21436257 is a wasteful number, since it uses less digits than its factorization.

21436257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 680.

The product of its digits is 10080, while the sum is 30.

The square root of 21436257 is about 4629.9305610344. The cubic root of 21436257 is about 277.7898149036.

Adding to 21436257 its reverse (75263412), we get a palindrome (96699669).

The spelling of 21436257 in words is "twenty-one million, four hundred thirty-six thousand, two hundred fifty-seven".