21451251361 has 2 divisors, whose sum is σ = 21451251362. Its totient is φ = 21451251360.

The previous prime is 21451251299. The next prime is 21451251383. The reversal of 21451251361 is 16315215412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13957059600 + 7494191761 = 118140^2 + 86569^2 .

It is a cyclic number.

It is not a de Polignac number, because 21451251361 - 2⁷ = 21451251233 is a prime.

It is not a weakly prime, because it can be changed into another prime (21451251761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10725625680 + 10725625681.

It is an arithmetic number, because the mean of its divisors is an integer number (10725625681).

Almost surely, 2^21451251361 is an apocalyptic number.

It is an amenable number.

21451251361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21451251361 is an equidigital number, since it uses as much as digits as its factorization.

21451251361 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7200, while the sum is 31.

Adding to 21451251361 its reverse (16315215412), we get a palindrome (37766466773).

The spelling of 21451251361 in words is "twenty-one billion, four hundred fifty-one million, two hundred fifty-one thousand, three hundred sixty-one".