21457761421 has 2 divisors, whose sum is σ = 21457761422. Its totient is φ = 21457761420.

The previous prime is 21457761373. The next prime is 21457761431. The reversal of 21457761421 is 12416775412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14657944900 + 6799816521 = 121070^2 + 82461^2 .

It is a cyclic number.

It is not a de Polignac number, because 21457761421 - 2⁷ = 21457761293 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21457761431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10728880710 + 10728880711.

It is an arithmetic number, because the mean of its divisors is an integer number (10728880711).

Almost surely, 2^21457761421 is an apocalyptic number.

It is an amenable number.

21457761421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21457761421 is an equidigital number, since it uses as much as digits as its factorization.

21457761421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 94080, while the sum is 40.

The spelling of 21457761421 in words is "twenty-one billion, four hundred fifty-seven million, seven hundred sixty-one thousand, four hundred twenty-one".