21961247 has 16 divisors (see below), whose sum is σ = 27762432. Its totient is φ = 16873920.

The previous prime is 21961243. The next prime is 21961249. The reversal of 21961247 is 74216912.

It is a happy number.

It is not a de Polignac number, because 21961247 - 2² = 21961243 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21961243) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3668 + ... + 7574.

It is an arithmetic number, because the mean of its divisors is an integer number (1735152).

Almost surely, 2^21961247 is an apocalyptic number.

21961247 is a deficient number, since it is larger than the sum of its proper divisors (5801185).

21961247 is a wasteful number, since it uses less digits than its factorization.

21961247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3998.

The product of its digits is 6048, while the sum is 32.

The square root of 21961247 is about 4686.2828553129. The cubic root of 21961247 is about 280.0393099571.

It can be divided in two parts, 2196 and 1247, that added together give a palindrome (3443).

The spelling of 21961247 in words is "twenty-one million, nine hundred sixty-one thousand, two hundred forty-seven".