20921371 has 2 divisors, whose sum is σ = 20921372. Its totient is φ = 20921370.

The previous prime is 20921363. The next prime is 20921377. The reversal of 20921371 is 17312902.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20921371 - 2³ = 20921363 is a prime.

It is not a weakly prime, because it can be changed into another prime (20921377) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10460685 + 10460686.

It is an arithmetic number, because the mean of its divisors is an integer number (10460686).

Almost surely, 2^20921371 is an apocalyptic number.

20921371 is a deficient number, since it is larger than the sum of its proper divisors (1).

20921371 is an equidigital number, since it uses as much as digits as its factorization.

20921371 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 20921371 is about 4573.9885220669. The cubic root of 20921371 is about 275.5476513503.

The spelling of 20921371 in words is "twenty million, nine hundred twenty-one thousand, three hundred seventy-one".