21403261 has 4 divisors (see below), whose sum is σ = 23349024. Its totient is φ = 19457500.

The previous prime is 21403259. The next prime is 21403273. The reversal of 21403261 is 16230412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21403261 - 2¹ = 21403259 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21403211) 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, 972865 + ... + 972886.

It is an arithmetic number, because the mean of its divisors is an integer number (5837256).

Almost surely, 2^21403261 is an apocalyptic number.

It is an amenable number.

21403261 is a deficient number, since it is larger than the sum of its proper divisors (1945763).

21403261 is a wasteful number, since it uses less digits than its factorization.

21403261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1945762.

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21403261 is about 4626.3658523727. The cubic root of 21403261 is about 277.6472113435.

Adding to 21403261 its reverse (16230412), we get a palindrome (37633673).

The spelling of 21403261 in words is "twenty-one million, four hundred three thousand, two hundred sixty-one".