21470831 has 2 divisors, whose sum is σ = 21470832. Its totient is φ = 21470830.

The previous prime is 21470821. The next prime is 21470837. The reversal of 21470831 is 13807412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21470831 - 2¹⁰ = 21469807 is a prime.

It is a super-2 number, since 2×21470831² = 921993167661122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21470831.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21470837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10735415 + 10735416.

It is an arithmetic number, because the mean of its divisors is an integer number (10735416).

Almost surely, 2^21470831 is an apocalyptic number.

21470831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21470831 is an equidigital number, since it uses as much as digits as its factorization.

21470831 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 21470831 is about 4633.6628060315. The cubic root of 21470831 is about 277.9390814191.

The spelling of 21470831 in words is "twenty-one million, four hundred seventy thousand, eight hundred thirty-one".