21990631 has 8 divisors (see below), whose sum is σ = 23797424. Its totient is φ = 20200320.

The previous prime is 21990623. The next prime is 21990643. The reversal of 21990631 is 13609912.

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

It is a cyclic number.

It is not a de Polignac number, because 21990631 - 2³ = 21990623 is a prime.

It is a super-2 number, since 2×21990631² = 967175703556322, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21990593 and 21990602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21990611) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1266 + ... + 6751.

It is an arithmetic number, because the mean of its divisors is an integer number (2974678).

Almost surely, 2^21990631 is an apocalyptic number.

21990631 is a deficient number, since it is larger than the sum of its proper divisors (1806793).

21990631 is a wasteful number, since it uses less digits than its factorization.

21990631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8241.

The product of its (nonzero) digits is 2916, while the sum is 31.

The square root of 21990631 is about 4689.4169147134. The cubic root of 21990631 is about 280.1641511958.

The spelling of 21990631 in words is "twenty-one million, nine hundred ninety thousand, six hundred thirty-one".