21621772267517 has 2 divisors, whose sum is σ = 21621772267518. Its totient is φ = 21621772267516.

The previous prime is 21621772267499. The next prime is 21621772267547. The reversal of 21621772267517 is 71576227712612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14045262785401 + 7576509482116 = 3747701^2 + 2752546^2 .

It is a cyclic number.

It is not a de Polignac number, because 21621772267517 - 2¹⁸ = 21621772005373 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21621772267547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10810886133758 + 10810886133759.

It is an arithmetic number, because the mean of its divisors is an integer number (10810886133759).

Almost surely, 2^{21621772267517} is an apocalyptic number.

It is an amenable number.

21621772267517 is a deficient number, since it is larger than the sum of its proper divisors (1).

21621772267517 is an equidigital number, since it uses as much as digits as its factorization.

21621772267517 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6914880, while the sum is 56.

The spelling of 21621772267517 in words is "twenty-one trillion, six hundred twenty-one billion, seven hundred seventy-two million, two hundred sixty-seven thousand, five hundred seventeen".