21501401 has 2 divisors, whose sum is σ = 21501402. Its totient is φ = 21501400.

The previous prime is 21501377. The next prime is 21501451. The reversal of 21501401 is 10410512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19811401 + 1690000 = 4451^2 + 1300^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21501401 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21501451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10750700 + 10750701.

It is an arithmetic number, because the mean of its divisors is an integer number (10750701).

Almost surely, 2^21501401 is an apocalyptic number.

It is an amenable number.

21501401 is a deficient number, since it is larger than the sum of its proper divisors (1).

21501401 is an equidigital number, since it uses as much as digits as its factorization.

21501401 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21501401 is about 4636.9603190021. The cubic root of 21501401 is about 278.0709280229.

Adding to 21501401 its reverse (10410512), we get a palindrome (31911913).

The spelling of 21501401 in words is "twenty-one million, five hundred one thousand, four hundred one".