21407261 has 2 divisors, whose sum is σ = 21407262. Its totient is φ = 21407260.

The previous prime is 21407257. The next prime is 21407263. The reversal of 21407261 is 16270412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16048036 + 5359225 = 4006^2 + 2315^2 .

It is a cyclic number.

It is not a de Polignac number, because 21407261 - 2² = 21407257 is a prime.

Together with 21407263, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21407263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10703630 + 10703631.

It is an arithmetic number, because the mean of its divisors is an integer number (10703631).

Almost surely, 2^21407261 is an apocalyptic number.

It is an amenable number.

21407261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21407261 is an equidigital number, since it uses as much as digits as its factorization.

21407261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21407261 is about 4626.7981369409. The cubic root of 21407261 is about 277.6645065221.

Adding to 21407261 its reverse (16270412), we get a palindrome (37677673).

The spelling of 21407261 in words is "twenty-one million, four hundred seven thousand, two hundred sixty-one".