21428577 has 16 divisors (see below), whose sum is σ = 32486080. Its totient is φ = 13952736.

The previous prime is 21428549. The next prime is 21428579. The reversal of 21428577 is 77582412.

It is a de Polignac number, because none of the positive numbers 2^k-21428577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21428579) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8068 + ... + 10389.

It is an arithmetic number, because the mean of its divisors is an integer number (2030380).

Almost surely, 2^21428577 is an apocalyptic number.

21428577 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21428577 is a deficient number, since it is larger than the sum of its proper divisors (11057503).

21428577 is a wasteful number, since it uses less digits than its factorization.

21428577 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18509 (or 18503 counting only the distinct ones).

The product of its digits is 31360, while the sum is 36.

The square root of 21428577 is about 4629.1011006458. The cubic root of 21428577 is about 277.7566362161.

The spelling of 21428577 in words is "twenty-one million, four hundred twenty-eight thousand, five hundred seventy-seven".