21520690 has 8 divisors (see below), whose sum is σ = 38737260. Its totient is φ = 8608272.

The previous prime is 21520687. The next prime is 21520693. The reversal of 21520690 is 9602512.

It is an interprime number because it is at equal distance from previous prime (21520687) and next prime (21520693).

It can be written as a sum of positive squares in 2 ways, for example, as 21446161 + 74529 = 4631^2 + 273^2 .

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

It is a super-2 number, since 2×21520690² = 926280196152200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21520693) 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, 1076025 + ... + 1076044.

Almost surely, 2^21520690 is an apocalyptic number.

21520690 is a deficient number, since it is larger than the sum of its proper divisors (17216570).

21520690 is a wasteful number, since it uses less digits than its factorization.

21520690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2152076.

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 21520690 is about 4639.0397713320. The cubic root of 21520690 is about 278.1540560478.

It can be divided in two parts, 215206 and 90, that added together give a square (215296 = 464²).

The spelling of 21520690 in words is "twenty-one million, five hundred twenty thousand, six hundred ninety".