21651421022521 has 2 divisors, whose sum is σ = 21651421022522. Its totient is φ = 21651421022520.

The previous prime is 21651421022509. The next prime is 21651421022533. The reversal of 21651421022521 is 12522012415612.

It is a balanced prime because it is at equal distance from previous prime (21651421022509) and next prime (21651421022533).

It can be written as a sum of positive squares in only one way, i.e., 16095052754496 + 5556368268025 = 4011864^2 + 2357195^2 .

It is a cyclic number.

It is not a de Polignac number, because 21651421022521 - 2⁵ = 21651421022489 is a prime.

It is not a weakly prime, because it can be changed into another prime (21651421022551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10825710511260 + 10825710511261.

It is an arithmetic number, because the mean of its divisors is an integer number (10825710511261).

Almost surely, 2^{21651421022521} is an apocalyptic number.

It is an amenable number.

21651421022521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21651421022521 is an equidigital number, since it uses as much as digits as its factorization.

21651421022521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19200, while the sum is 34.

The spelling of 21651421022521 in words is "twenty-one trillion, six hundred fifty-one billion, four hundred twenty-one million, twenty-two thousand, five hundred twenty-one".