21290690 has 8 divisors (see below), whose sum is σ = 38323260. Its totient is φ = 8516272.

The previous prime is 21290653. The next prime is 21290693. The reversal of 21290690 is 9609212.

21290690 = 2663² + 2664² + 2665².

It can be written as a sum of positive squares in 2 ways, for example, as 20367169 + 923521 = 4513^2 + 961^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21290690² = 906586961352200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21290693) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1064525 + ... + 1064544.

Almost surely, 2^21290690 is an apocalyptic number.

21290690 is a deficient number, since it is larger than the sum of its proper divisors (17032570).

21290690 is a wasteful number, since it uses less digits than its factorization.

21290690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2129076.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 21290690 is about 4614.1835680866. The cubic root of 21290690 is about 277.1595912493.

The spelling of 21290690 in words is "twenty-one million, two hundred ninety thousand, six hundred ninety".