20921507 has 2 divisors, whose sum is σ = 20921508. Its totient is φ = 20921506.

The previous prime is 20921501. The next prime is 20921519. The reversal of 20921507 is 70512902.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20921507 - 2¹⁰ = 20920483 is a prime.

It is not a weakly prime, because it can be changed into another prime (20921501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10460753 + 10460754.

It is an arithmetic number, because the mean of its divisors is an integer number (10460754).

Almost surely, 2^20921507 is an apocalyptic number.

20921507 is a deficient number, since it is larger than the sum of its proper divisors (1).

20921507 is an equidigital number, since it uses as much as digits as its factorization.

20921507 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1260, while the sum is 26.

The square root of 20921507 is about 4574.0033887176. The cubic root of 20921507 is about 275.5482484176.

The spelling of 20921507 in words is "twenty million, nine hundred twenty-one thousand, five hundred seven".