21545690 has 16 divisors (see below), whose sum is σ = 38880000. Its totient is φ = 8596560.

The previous prime is 21545683. The next prime is 21545707. The reversal of 21545690 is 9654512.

It is a happy number.

It is a super-2 number, since 2×21545690² = 928433515152200, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1811 + ... + 6809.

It is an arithmetic number, because the mean of its divisors is an integer number (2430000).

Almost surely, 2^21545690 is an apocalyptic number.

21545690 is a deficient number, since it is larger than the sum of its proper divisors (17334310).

21545690 is a wasteful number, since it uses less digits than its factorization.

21545690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5437.

The product of its (nonzero) digits is 10800, while the sum is 32.

The square root of 21545690 is about 4641.7335123852. The cubic root of 21545690 is about 278.2617223670.

The spelling of 21545690 in words is "twenty-one million, five hundred forty-five thousand, six hundred ninety".