20645690 has 64 divisors (see below), whose sum is σ = 42577920. Its totient is φ = 7153920.

The previous prime is 20645683. The next prime is 20645707. The reversal of 20645690 is 9654602.

It is a super-2 number, since 2×20645690² = 852489031152200, which contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 189356 + ... + 189464.

It is an arithmetic number, because the mean of its divisors is an integer number (665280).

Almost surely, 2^20645690 is an apocalyptic number.

20645690 is an abundant number, since it is smaller than the sum of its proper divisors (21932230).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20645690 is a wasteful number, since it uses less digits than its factorization.

20645690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207.

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 20645690 is about 4543.7528541944. The cubic root of 20645690 is about 274.3319985086.

The spelling of 20645690 in words is "twenty million, six hundred forty-five thousand, six hundred ninety".