20921501 has 2 divisors, whose sum is σ = 20921502. Its totient is φ = 20921500.

The previous prime is 20921479. The next prime is 20921507. The reversal of 20921501 is 10512902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20921476 + 25 = 4574^2 + 5^2 .

It is a cyclic number.

It is not a de Polignac number, because 20921501 - 2¹⁰ = 20920477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20921507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10460750 + 10460751.

It is an arithmetic number, because the mean of its divisors is an integer number (10460751).

Almost surely, 2^20921501 is an apocalyptic number.

It is an amenable number.

20921501 is a deficient number, since it is larger than the sum of its proper divisors (1).

20921501 is an equidigital number, since it uses as much as digits as its factorization.

20921501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 180, while the sum is 20.

The square root of 20921501 is about 4574.0027328370. The cubic root of 20921501 is about 275.5482220764.

The spelling of 20921501 in words is "twenty million, nine hundred twenty-one thousand, five hundred one".