21421400251 has 2 divisors, whose sum is σ = 21421400252. Its totient is φ = 21421400250.

The previous prime is 21421400249. The next prime is 21421400291. The reversal of 21421400251 is 15200412412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21421400251 - 2¹ = 21421400249 is a prime.

Together with 21421400249, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21421400201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710700125 + 10710700126.

It is an arithmetic number, because the mean of its divisors is an integer number (10710700126).

Almost surely, 2^21421400251 is an apocalyptic number.

21421400251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21421400251 is an equidigital number, since it uses as much as digits as its factorization.

21421400251 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 640, while the sum is 22.

Adding to 21421400251 its reverse (15200412412), we get a palindrome (36621812663).

The spelling of 21421400251 in words is "twenty-one billion, four hundred twenty-one million, four hundred thousand, two hundred fifty-one".