21623691 has 16 divisors (see below), whose sum is σ = 30464000. Its totient is φ = 13605408.

The previous prime is 21623681. The next prime is 21623699. The reversal of 21623691 is 19632612.

It is not a de Polignac number, because 21623691 - 2⁶ = 21623627 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21623699) 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, 19350 + ... + 20436.

It is an arithmetic number, because the mean of its divisors is an integer number (1904000).

Almost surely, 2^21623691 is an apocalyptic number.

21623691 is a deficient number, since it is larger than the sum of its proper divisors (8840309).

21623691 is a wasteful number, since it uses less digits than its factorization.

21623691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1458.

The product of its digits is 3888, while the sum is 30.

The square root of 21623691 is about 4650.1280627527. The cubic root of 21623691 is about 278.5971112228.

The spelling of 21623691 in words is "twenty-one million, six hundred twenty-three thousand, six hundred ninety-one".