21891475 has 6 divisors (see below), whose sum is σ = 27145460. Its totient is φ = 17513160.

The previous prime is 21891473. The next prime is 21891479. The reversal of 21891475 is 57419812.

It is not a de Polignac number, because 21891475 - 2¹ = 21891473 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21891473) 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 5 ways as a sum of consecutive naturals, for example, 437805 + ... + 437854.

Almost surely, 2^21891475 is an apocalyptic number.

21891475 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21891475 is a deficient number, since it is larger than the sum of its proper divisors (5253985).

21891475 is an equidigital number, since it uses as much as digits as its factorization.

21891475 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 875669 (or 875664 counting only the distinct ones).

The product of its digits is 20160, while the sum is 37.

The square root of 21891475 is about 4678.8326535579. The cubic root of 21891475 is about 279.7424289502.

It can be divided in two parts, 21891 and 475, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 21891475 in words is "twenty-one million, eight hundred ninety-one thousand, four hundred seventy-five".