20802421 has 2 divisors, whose sum is σ = 20802422. Its totient is φ = 20802420.

The previous prime is 20802401. The next prime is 20802427. The reversal of 20802421 is 12420802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20566225 + 236196 = 4535^2 + 486^2 .

It is a cyclic number.

It is not a de Polignac number, because 20802421 - 2⁹ = 20801909 is a prime.

It is a super-2 number, since 2×20802421² = 865481438922482, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20802427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10401210 + 10401211.

It is an arithmetic number, because the mean of its divisors is an integer number (10401211).

Almost surely, 2^20802421 is an apocalyptic number.

It is an amenable number.

20802421 is a deficient number, since it is larger than the sum of its proper divisors (1).

20802421 is an equidigital number, since it uses as much as digits as its factorization.

20802421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 256, while the sum is 19.

The square root of 20802421 is about 4560.9671123568. The cubic root of 20802421 is about 275.0244430064.

The spelling of 20802421 in words is "twenty million, eight hundred two thousand, four hundred twenty-one".