20821907 has 2 divisors, whose sum is σ = 20821908. Its totient is φ = 20821906.

The previous prime is 20821897. The next prime is 20821909. The reversal of 20821907 is 70912802.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20821907 is a prime.

It is a super-2 number, since 2×20821907² = 867103622233298, which contains 22 as substring.

Together with 20821909, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_1319393 and since 20821907 and 1319393 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20821907.

It is not a weakly prime, because it can be changed into another prime (20821909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10410953 + 10410954.

It is an arithmetic number, because the mean of its divisors is an integer number (10410954).

Almost surely, 2^20821907 is an apocalyptic number.

20821907 is a deficient number, since it is larger than the sum of its proper divisors (1).

20821907 is an equidigital number, since it uses as much as digits as its factorization.

20821907 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 20821907 is about 4563.1027820990. The cubic root of 20821907 is about 275.1102896464.

The spelling of 20821907 in words is "twenty million, eight hundred twenty-one thousand, nine hundred seven".