20721461 has 2 divisors, whose sum is σ = 20721462. Its totient is φ = 20721460.

The previous prime is 20721439. The next prime is 20721479. The reversal of 20721461 is 16412702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20566225 + 155236 = 4535^2 + 394^2 .

It is a cyclic number.

It is not a de Polignac number, because 20721461 - 2⁶ = 20721397 is a prime.

It is equal to p_1313474 and since 20721461 and 1313474 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20721401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10360730 + 10360731.

It is an arithmetic number, because the mean of its divisors is an integer number (10360731).

Almost surely, 2^20721461 is an apocalyptic number.

It is an amenable number.

20721461 is a deficient number, since it is larger than the sum of its proper divisors (1).

20721461 is an equidigital number, since it uses as much as digits as its factorization.

20721461 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 20721461 is about 4552.0831495042. The cubic root of 20721461 is about 274.6671940939.

The spelling of 20721461 in words is "twenty million, seven hundred twenty-one thousand, four hundred sixty-one".