21628501 has 2 divisors, whose sum is σ = 21628502. Its totient is φ = 21628500.

The previous prime is 21628469. The next prime is 21628553. The reversal of 21628501 is 10582612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11737476 + 9891025 = 3426^2 + 3145^2 .

It is a cyclic number.

It is not a de Polignac number, because 21628501 - 2⁵ = 21628469 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21628001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10814250 + 10814251.

It is an arithmetic number, because the mean of its divisors is an integer number (10814251).

Almost surely, 2^21628501 is an apocalyptic number.

It is an amenable number.

21628501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21628501 is an equidigital number, since it uses as much as digits as its factorization.

21628501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 21628501 is about 4650.6452240522. The cubic root of 21628501 is about 278.6177668509.

The spelling of 21628501 in words is "twenty-one million, six hundred twenty-eight thousand, five hundred one".