21551690 has 16 divisors (see below), whose sum is σ = 40480128. Its totient is φ = 8245776.

The previous prime is 21551671. The next prime is 21551693. The reversal of 21551690 is 9615512.

It is a super-2 number, since 2×21551690² = 928950683712200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21551693) by changing a digit.

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, 46622 + ... + 47081.

It is an arithmetic number, because the mean of its divisors is an integer number (2530008).

Almost surely, 2^21551690 is an apocalyptic number.

21551690 is a deficient number, since it is larger than the sum of its proper divisors (18928438).

21551690 is a wasteful number, since it uses less digits than its factorization.

21551690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93733.

The product of its (nonzero) digits is 2700, while the sum is 29.

The square root of 21551690 is about 4642.3797776571. The cubic root of 21551690 is about 278.2875498895.

The spelling of 21551690 in words is "twenty-one million, five hundred fifty-one thousand, six hundred ninety".